Cream butter and sugar; add eggs, sour cream, and vanilla. Beat well (with electric mixer) and gradually add sifted flour, baking powder, and baking soda. When mixture is too thick to beat, stir with spoon until well mixed. Place half the mixture in buttered 9 inch tube spring form pan and sprinkle with half of the topping mixture. Place remaining dough on top and sprinkle with remaining topping. Bake in moderate oven (350 degrees) for an hour or until knife comes out clean. Sprinkle with powdered sugar when still hot and let cool 15 to 20 minutes before cutting.