Follow the directions on your package to pop the popcorn.

Preheat the oven to 250 F.

Line a baking pan with sides with aluminum foil.

Place the butter in a glass bowl and melt it in the microwave. Melt it in 15-second intervals and stir in-between.  

Add the sugar, salt, cinnamon, and vanilla extract to the bowl of melted butter. Stir thoroughly.

Heat up the mixture in 10-second intervals until it is fully melted and combined. Stir every 10 seconds. This shouldn’t take more than about 30 seconds in the microwave.

Slowly pour the mixture over the popcorn and mix until the popcorn is completely coated.

Spread the popcorn evenly on the baking pan. 

Bake it in the oven for 10 minutes.

After 10 minutes turn the oven off but don’t open the oven.

Leave it to rest in the oven for 20 minutes.

Remove it from the oven. Leave to fully cool, or enjoy warm if you’d prefer, and you’re all set.