Put the butter into a pot on the stove. Turn on medium-low heat and stir until the butter melts and foams.

After a short time, the butter will turn golden, and brown specks will appear.

Once the foam disappears and the butter gets a nutty smell, take the pot off the heat. (the coloring should be a golden brown but not black.)

Stir in the vanilla extract. (there might be a bit of foam that forms during this.)

While the butter cools slightly, mix the cinnamon and sugar in a different bowl.

Slowly drizzle the melted butter over the top of the popped popcorn. (leave any dark brown specks or remains at the bottom of the pot.)

Carefully fold the popcorn to coat. Sprinkle 1/2 of the cinnamon sugar mixture over the popcorn and stir carefully.

Repeat with the rest of the cinnamon sugar mixture.

Serve.