(Note: Make base for icing the night before making cake.) Preheat oven 350 degrees. Grease and dust with cocoa three 9 inch cake pans. Cream butter and sugar, add egg and beat until fluffy. Make paste from cocoa and vinegar and add to butter mixture. Sift salt and soda with flour. Add to mixture alternately with buttermilk. Add vanilla and coloring. Bake at 350 degrees about 25-30 minutes. Makes 3 layers. White Icing for Red Velvet Cake 1/4 cup flour 1 cup sweet milk Cook over low heat until smooth paste and let cool. Cover and put in the refrigerator over night. Cream together: 1 stick margarine 1/2 cup Crisco 1 cup white sugar 1 t. vanilla Beat until fluffy. Add paste and beat together and spread on tops only of cool cakes. Refrigerate!