Preheat oven to 350 degrees F. Grease and flour two 9 x 1 1/2-inch round baking pans or one 9 x 13 inch pan, or line cupcake tins (makes 24 cupcakes); set aside.
Sift together flour, Clabber Girl Baking Powder, salt and cocoa; set aside. In a large mixing bowl, cream oil and sugar. Add eggs to creamed mixture, one at a time, beating well after each addition. Add food coloring to creamed mixture, mix until well blended; set aside. In a separate bowl, combine buttermilk and baking soda, mixing well; add to oil and sugar mixture, alternating with dry ingredients. Add vinegar and vanilla, mix well. Spoon into prepared pans.
Bake at 350 degrees F. for 25 to 30 minutes.
To prepare cream cheese frosting: Combine cream cheese, margarine or butter, and vanilla in a mixing bowl. Beat until well blended and smooth. Gradually add powdered sugar while beating. Frosting should be thick and smooth. If necessary, add more powdered sugar until the frosting is firm.
Frost the cake only after it is completely cooled. Makes 1 two-layer cake or one 9 x13-inch cake or 24 cupcakes.