Using a 10 inch tube pan, prepare:grease and flour set aside. Preheat oven 325.
Cake: In mixing bowl combine, butter, shortening and sugar and cream until light and fluffy. Add eggs one at a time beating after each addition. Stir in the food coloring and vanilla. Stir together in seperate bowl flour and salt; add this to the creamed mixture alternately with the milk, beating well. Pour batter into prepared pan. Bake 1 hour 20 minutes, check for doneness. Cool cake in pan at least 15 minutes, turn out onto rack to cool completely.
I just use a confectioners sugar drizzle with milk and vanilla. I don't frost the whole cake but I'm sure it would be great. To me it wouldn't be a pound cake frosting the whole thing. Do what your taste calls for, have fun with it. Enjoy