Peanut Butter Cup Chocolate Cake Ingredients Peanut Butter Cup Chocolate Cake 1 1/2 cups all purpose flour 1/4 cup cocoa powder 1 cup sugar 1 tsp baking soda 1/2 tsp salt 1 cup buttermilk 1/4 cup butter, melted and cooled 1 tsp apple cider vinegar 1 tsp vanilla extract Butter Filling 1/4 cup butter,