In a large mixing bowl, cream butter and 2 cups of sugar until fluffy. Add vanilla. Add eggs, one at a time, beating well after each addition. Combine flour, baking powder, soda and salt. Add alternately with sour cream, beating just enough after each addition to keep batter smooth. Spoon 1/3 of batter into a greased 10 inch tube pan. Combine cinnamon, nuts and remaining sugar. Sprinkle 1/3 over batter in pan. Repeat layers 2 more times. Bake at 350 degrees for 60-70 minutes or until cake tests done. Cool for 10 minutes. Remove from pan to cool completely. Butter top and let melt.