In a large saucepan, heat the buttermilk and butter until barely bubbling. Remove from heat and quickly stir in flour mixture and remaining ingredients until smooth. Pour batter into lightly greased 10x15" baking pan. Bake at 350° for 20-25 minutes or until cake is golden brown and tests done in the center. Allow to cool for 15 minutes.
Spread frosting over warm cake and then sprinkle with nuts, if desired.
TIP: If you can't find the frosting, substitute with cream cheese frosting with 1/2 teaspoon almond extract added.