In a bowl, mix together the softened butter, minced garlic, lemon juice, thyme, salt and pepper until fully combined. Set aside. You can store in the fridge for up to 2 weeks!
Preheat the oven to 425°F.
In a small bowl, mix together the salt, pepper, garlic powder, paprika, cumin, and cayenne.
Pat the chicken breasts dry with a paper towel and season liberally on both sides with the spice mixture.
Heat a large cast iron skillet over medium high heat. Add in just enough oil to coat the bottom of the pan (about 1 tablespoon).
Sear the chicken breasts on one side for 5 minutes. Then flip and immediately transfer the cast iron pan to the preheated oven. Bake at 425°F for 10-15 minutes or until the chicken is fully cooked through. [Smaller, thinner breasts will only have to bake for 5-10 minutes, but thicker breasts will need 15-20 minutes.]
Use an instant thermometer to check when the chicken is done so that it doesn't get overcooked! Chicken breasts should be cooked to an internal temperature of 165°F, but I like to pull them out around 160-162°F because they'll continue cooking as they rest.
Remove the chicken from the oven and top each breast about a tablespoon of garlic herb butter.
Let the chicken rest for at least 5-10 minutes before slicing.
Store in an airtight container at room temperature for up to 4 days. Add on top of salads or pasta, or reheat at 350°F for about 10 minutes.