In a large bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Combine flour, baking powder and soda; add to creamed mixture alternately with sour cream, beating well after each addition.
Spoon half of batter into a greased 10-in. tube pan. Combine topping ingredients; sprinkle half over batter. Add remaining batter and topping.
Bake at 350° for 45 minutes or until done. Cool in pan on wire rack for 10 minutes before removing from pan to cool completely. For icing, combine all ingredients until smooth; drizzle over cake.