CAKE: Cream sugar and butter thoroughly. Add eggs, one at a time beating well after each addition.
Sift flour with baking powder and salt. Add dry ingredients to batter alternately with milk.
Bake in 3 greased, flour dusted (8 or 9-inch) layer cake tins for about 25 minutes at 350 degrees. For thicker layers, bake in 2 cake tins.
CARAMEL ICING: Combine sugars, buttermilk and butter; cook until soft ball forms in cold water. Remove from heat; add vanilla and soda. Beat until creamy enough to spread. Do not overbeat. The secret of the icing is in the buttermilk.