Using an air popper, pop the popcorn according to manufacturer instructions (see notes for stove-top popcorn), then dump into a large serving bowl.
In a small pot, melt butter over medium heat, stirring frequently. Watch closely for the butter to develop brown specs and a nutty aroma, about 5 minutes. Once you start seeing brown specs, let cook for just a few seconds longer until the butter is golden (watch very carefully or it will burn). Remove from the heat and let cool for about 10 minutes. Then pour over the popcorn.
Toss the popcorn until it's evenly coated and season with salt to taste.
Notes
Stove-top popcorn: In a large stock pot or dutch oven (with a lid) heat the ¼ cup of vegetable oil or coconut oil and 3 popcorn kernels over medium heat (don't forget to put the lid on). Once those kernels pop (about 2-3 minutes) add in the rest of the popcorn kernels and give the pot a shake to evenly coat the kernels in oil. Cover the pot and continue to cook the popcorn, giving the pot an occasional shake to ensure it doesn't burn. Once the kernels start to pop, watch closely until the popping sounds slow down to one pop every 2-3 seconds. Remove the lid and dump the popcorn into a large serving bowl.Popcorn will keep in an airtight container for up to 3 days but tastes best when eaten the same day.