In a large bowl, cream butter and 2 cups sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Combine the flour, baking powder, baking soda and salt; add to creamed mixture alternately with sour cream.
Spoon a third of the batter into a greased and floured 10-in. tube pan. Combine the cinnamon, nuts and remaining sugar; sprinkle a third over batter. Repeat layers twice.
Bake at 350° for 65-70 minutes or until toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack. Yield: 10-12 servings.