Process the cheddar cheese powder, "parmesan" cheese powder, nutritional yeast, buttermilk powder, and kosher salt in a food processor to a fine, granular powder.
Place the oil and popcorn kernels in a large, 6-quart metal mixing bowl. Cover with heavy-duty aluminum foil and poke 10 slits in the top with a knife.
Place the bowl over medium heat and shake constantly using a pair of tongs or kitchen towels to hold the bowl. Continue shaking until the popcorn finishes popping, approximately 3 minutes.
Remove the bowl from the heat and carefully remove the foil.
Slowly drizzle the melted butter over the popcorn while spinning the bowl. Add the cheese mixture, re-cover with aluminum foil, and shake the coat the popcorn with the cheese mixture. Serve immediately.