These key lime cupcakes are filled with homemade key lime curd and topped with tangy cream cheese frosting and graham cracker crumbs. They taste just like classic key lime pie but in cupcake form! They're the perfect summer treat!
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What are Key Limes?
Key limes are the smaller, sweeter cousin to regular limes. They're also known as the Mexican Lime or the West Indies Lime. They have a unique floral flavor that's tart without being too acidic.
In the US, key limes are in season from June to August so you can usually only find them at the grocery store during those months, which is why these key lime pie cupcakes are such a popular summer treat!
However, if you aren't lucky enough to find fresh key limes at the store, bottled key lime juice works great! Nellie & Joe's key lime juice is delicious and is sold at most grocery stores as well as amazon.
If you like key lime as much as I do, you might also like these key lime pie bars or these key lime pie macarons!
Ingredient Notes
You only need a few ingredients to make these key lime pie cupcakes!
Cake Flour - I always use cake flour in my cupcakes because it makes them super soft and tender, but all purpose flour also works great!
Sour Cream - I love adding sour cream to baked goods because it keeps them super light and moist! You can also substitute plain full-fat yogurt or whole milk instead.
Egg Yolks - You need egg yolks to help the key lime curd thicken. You can use the leftover egg whites to make macarons or meringues!
Key Lime Juice and Zest - The stars of the show! I always prefer baking with fresh key limes, but if you can't find them you can use bottled key lime juice and the zest from regular limes.
Graham Crackers - I like to garnish the key lime cupcakes with crushed graham crackers to add that classic key lime pie flavor.
The complete list of ingredients and amounts is located in the recipe card below.
How to Make Key Lime Curd
First make the key lime curd! You can check out my full post on how to make lemon curd for extra tips and tricks! I also talk about how to make a double boiler and why you should never use metal when making lemon/lime curd!
Note: I highly recommend making the key lime curd the night before you make the cupcakes so that it has time to fully cool/set.
Create a double boiler by bringing 1-2 inches of water to a simmer in a small saucepan. Place a heatproof glass bowl on top and make sure it's not touching the water.
Add the egg yolks, sugar, key lime juice, key lime zest, and salt into the top of your double boiler.
Whisk until completely combined and then continue to whisk as the key lime curd cooks (constant whisking prevents the curd from curdling). Continue to whisk the key lime curd for 10-15 minutes or until it becomes thick and paler in color (it should be similar to the consistency of hollandaise sauce). If the lime curd isn’t thickening, turn up the heat and constantly whisk. *If your lime curd still is not thickening with the double boiler, you can transfer to a pot to cook over direct heat for a couple minutes until it fully thickens.
Once thickened, remove the glass bowl from the heat. Cut the butter into chunks and whisk into the key lime curd until fully combined and smooth.
If desired, pass through fine mesh strainer and then pour into a glass jar. Let cool to room temperature and then cover and store in the fridge for up to a week.
You'll almost certainly have some leftover key lime curd, so you can serve it with homemade crepes or scones!
How to Make Key Lime Cupcakes
Preheat the oven to 350°F and line a 12 cup pan with cupcake liners.
In a medium bowl, add the sugar and key lime zest. Then use your fingers to gently massage the key lime zest into the sugar (this is optional, but helps infuse the sugar with even more key lime flavor).
Whisk the cake flour, baking powder, and salt together in a large bowl.
In a separate bowl, whisk the melted butter and flavored sugar.
Add in the eggs and key lime juice and whisk until fully combined.
Stir in about half of the flour mixture. Then stir in the sour cream and the rest of the flour mixture and mix until fully combined.
Pour about ¼ cup of batter into each cupcake liner (they should be about halfway full).
Bake at 350°F for 18-22 minutes or until a cake tester comes out clean.
Remove from pan and let cool on wire rack. Let cupcakes cool completely before filling and frosting.
Use a cupcake corer to remove the center of each cupcake, then fill with 1-2 teaspoons of cooled key lime curd.
Frost cooled key lime cupcakes, then garnish with graham cracker crumbs, key lime slices, and key lime zest if desired!
Tips for the Best Baked Goods
Use room temperature ingredients! Always make sure ingredients like butter, eggs, milk, yogurt, etc. are at room temperature before baking (unless the recipe indicates otherwise)! This ensures they'll incorporate into the batter more easily and leads to overall better texture. Remove all ingredients from the fridge 30 minutes to an hour before baking for best results.
Measure your flour correctly! It's most accurate to use a kitchen scale, but if you're measuring by volume you want to spoon and level! Fluff up the flour a bit with a spoon, and then spoon flour into the measuring cup. Once it's overflowing, use the back of a knife to level it off. Don't ever pack flour into the measuring cup or you'll end up with way too much! Improperly measured flour can lead to dry, dense baked goods. [Measure cocoa powder the same way!]
Use an oven thermometer! Just because your oven says it's 350, doesn't mean it is! If you oven hasn't been calibrated recently, it can be as much as 30 degrees off, which will negatively affect all baked goods from cakes to macarons! An oven thermometer is the easiest/cheapest way to ensure your oven is always at the proper temperature.
Make sure you baking powder is fresh! Baking powder is important for helping baked goods rise properly, but it has a relatively short shelf life once opened, so it's one of the few items I never buy in bulk! To test if your baking powder is still fresh, add a small amount to boiling water. If it bubbles it's still good to use, but if not it's time to toss it!
Cupcake Decorating Tips
Make sure you let the cupcakes cool completely before frosting!!
Use a cupcake corer to easily remove the center of your cupcakes before filling with key lime curd.
For these big beautiful cream cheese frosting swirls on these key lime pie cupcakes, I use the large round tip from this decorating kit. The tips are much larger than standard sizes and so fun for decorating cupcakes!
After frosting, garnish with graham cracker crumbs, key lime slices, and key lime zest if desired!
Recipe FAQ's
These cupcakes will last in the fridge for up to 3 days. However, they taste best when served at room temperature! I like to let them sit at room temperature for about an hour before serving. But I recommend waiting to top with key lime slices until immediately before serving!
You can, but I don't recommend it. Key limes have a different, sweeter flavor than regular limes! But you can find bottled key lime juice in most grocery stores and online!
Tips for Success!
For best results I always recommend using weight measurements (especially when baking) because it's the most accurate. Kitchen scales are super affordable and also reduce the number of dishes you have to do! However, all my recipes also include US customary measurements for convince. Use this chart to convert measurements for common ingredients!
Substitutions: In all my recipes, I've included substitutions that I know will work, but I cannot guarantee results if you substitute ingredients that I have not recommended. [For example, granulated sugar and honey are indeed both sweeteners but they have very different properties so they can not always be swapped 1:1. Using honey in a cookie recipe that calls for granulated sugar will yield a giant mess.] In the recipe card you'll find links to the specific ingredients/brands that I use.
A note on salt: I almost exclusively use Diamond Crystal Kosher Salt because it's the best all-purpose salt for cooking and baking. If you're not using kosher salt, consult this handy guide for a conversion chart! When in doubt, if you're using table salt just reduce the amount by half for baked goods. When cooking, I prefer to under-salt because you can always add more! If you've over-salted, adding a little bit of acid (like lemon juice) can help.
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Recipe Card
Key Lime Cupcakes
Special Equipment
- double boiler
Ingredients
Key Lime Curd
- ½ cup granulated sugar
- 1 teaspoon key lime zest
- 3 large egg yolks
- ½ cup key lime juice
- ¼ teaspoon kosher salt
- ¼ cup unsalted butter
Cupcakes
- ½ cup unsalted butter, melted
- 1 cup granulated sugar
- 1 tablespoon key lime zest
- 2 large eggs, room temperature
- 2 tablespoons key lime juice
- 1 ½ cups cake flour, substitute all purpose flour
- 1 ½ teaspoons baking powder
- ½ teaspoon kosher salt
- ½ cup sour cream, substitute plain full-fat yogurt
Cream Cheese Frosting
- 1 cup unsalted butter, room temperature
- 4 ounces cream cheese, room temperature
- 3 ½ cups powdered sugar
- 2 tablespoons key lime juice
Garnish
- graham cracker crumbs
- key lime slices
- key lime zest
Instructions
Key Lime Curd
- I recommend making the key lime curd the night before you make the cupcakes so that it has time to fully cool/set.
- Create a double boiler by bringing 1-2 inches of water to a simmer in a small saucepan. Place a heatproof glass bowl on top and make sure it's not touching the water.
- Add the egg yolks, sugar, key lime juice, key lime zest, and salt into the top of your double boiler.
- Whisk until completely combined and then continue to whisk as the key lime curd cooks (constant whisking prevents the curd from curdling). Continue to whisk the key lime curd for 10-15 minutes or until it becomes thick and paler in color (it should be similar to the consistency of hollandaise sauce). If the lime curd isn’t thickening, turn up the heat and constantly whisk. *If your lime curd still is not thickening with the double boiler, you can transfer to a pot to cook over direct heat for a couple minutes until it fully thickens.
- Once thickened, remove the glass bowl from the heat. Cut the butter into chunks and whisk into the key lime curd until fully combined and smooth.
- If desired, pass through fine mesh strainer and then pour into a glass jar.
- Let cool to room temperature and then cover and store in the fridge for up to a week. You'll almost certainly have some leftover key lime curd, so you can serve it with homemade crepes or scones!
Cupcakes
- Preheat the oven to 350°F and line a 12 cup pan with cupcake liners.
- In a medium bowl, add the sugar and key lime zest. Then use your fingers to gently massage the key lime zest into the sugar (this is optional, but helps infuse the sugar with even more key lime flavor).
- Whisk the cake flour, baking powder, and salt together in a large bowl.
- In a separate bowl, whisk the melted butter and flavored sugar.
- Add in the eggs and key lime juice and whisk until fully combined.
- Stir in about half of the flour mixture. Then stir in the sour cream and the rest of the flour mixture and mix until fully combined.
- Pour about ¼ cup of batter into each cupcake liner (they should be about halfway full).
- Bake at 350°F for 18-22 minutes or until a cake tester comes out clean.
- Remove from pan and let cool on wire rack. Let cupcakes cool completely before filling and frosting.
- Use a cupcake corer to remove the center of each cupcake, then fill with 1-2 teaspoons of cooled key lime curd.
Cream Cheese Frosting
- While the cupcakes are cooling, make the frosting.
- In a stand mixer fitted with the paddle attachment, cream together the softened butter and cream cheese until completely smooth.
- Then add in the powdered sugar and beat on slow until combined.
- Slowly add in the key lime juice until fully combined. Then beat the buttercream for 3-4 minutes on high speed until light and fluffy.
- Frost cooled key lime cupcakes, then garnish with graham cracker crumbs, key lime slices, and key lime zest if desired!
Notes
Nutrition
The nutritional information on this website is only an estimate and is provided for convenience and as a courtesy only. The accuracy of the nutritional information for any recipe on this site is not guaranteed.
Debbie says
I made these today….OH MY GOODNESS! So delicious. Will definitely be making them again.
Jessica says
Can this recipe be used to make a cake?
Kyleigh Sage says
Yes! This recipe convert to a 9 inch square cake or 8 inch round cake (or a 2 layer 6 inch round cake). But if you double it, it will make a 2 layer 8 inch cake. If you do 1 1/2 times the volume of the cupcake batter so it would also work as a 9x13 inch cake! For cakes you'll just have to increase the baking time (usually 25-35 minutes).
Swathi says
Key lime cupcakes are delicious, I have tried them, and my family enjoyed it.