Liquid Filling M

1/2 c. Softened butter 1/4 c. Brown Sugar 3/4 c. Granulated Sugar 1 Large Egg 1 tsp Vanilla Extract 1 1/2 c. Flour 2 tbsp Cocoa Powder 1/4 tsp Salt 1/4 tsp Baking Powder (high elevation: 1/16 tsp) 1/2 tsp Baking Soda (high elevation: 1/8 tsp) 1 tsp White Vinegar 1 1/2 tsp Red Food Colori