1/2 cup unsalted butter at room temperature 1 cup sugar 1 teaspoon distilled white vinegar 1 large egg 1 teaspoon vanilla extract 1 1/2 teaspoons red food coloring 1 1/2 cups all purpose flour 2 1/2 tablespoons cocoa 1 teaspoon cornstarch 3/4 teaspoon baking powder 1/4 teaspoon s