Heat together the margarine and Dr. Pepper until margarine is just melted. DO NOT BOIL! Sift together flour, sugar, cinnamon, salt and cocoa into mixing bowl. Combine eggs, buttermilk, soda and vanilla. Add the Dr.Pepper mixture to the dry ingredients and blend well. Add the egg mixture. Mix well. Pour into a sheet cake pan and bake at 180ºC or about 25 minutes or until cake tests done. About 5 minutes before the cake is done, start the frosting by heating together the margarine, cocoa and Dr. Pepper. Then stir in the nuts, vanilla and powdered sugar. Blend smooth. Spread evenly on the cake as soon as it is removed from the oven and is hot. This recipe makes very good cupcakes (about 36). From Mary Bowles, DNSR31A,from *Prodigy's Food and Wine Bulletin Board. ----