TOPPING
Mix the ingredients for the topping and set aside.
CAKE
Add the baking powder and flour and stir.
Cream together the butter and sugar. Add the eggs and vanilla; Mix until creamy. Add the sour cream and mix well. Add the flour mixture. Mix well.
Grease and flour a 13 X 9 - inch pan. Layer 1/2 of the batter and 1/2 of the topping mixture. Layer the remaider of the batter. Add the other 1/2 of the topping. Swirl the batter with a knif.
Bake at 350* for 45 to 50 minutes.