Preheat oven to 225F. Spray a large roasting pan with cooking spray.

Place popped popcorn in the roasting pan.

Salt the popcorn.

In a large saucepan, bring butter, brown sugar, corn syrup, and cream of tartar to a boil, stirring constantly.

Let boil for 5 min. on medium heat without stirring.

Remove the saucepan from heat and stir in vanilla and baking soda.

Pour over the popcorn and stir to coat.

Place the pan in the oven.

Stir every 15 min. so that the mixture does not burn. Bake for 1 hour. Stir well at the end.

Remove from the pan and let cool completely on parchment paper. Store in Ziploc bags or sealed containers. Yum!!