Preheat oven to 400ºF. Lightly grease a 10-inch bundt pan. Cream sugar and eggs. Add sour cream and butter, and beat well. Add flour, baking soda and baking powder; mix well. Stir in vanilla and chopped nuts. In a small bowl, mix the remaining ¼ cup white sugar and cinnamon. Pour half the batter into the prepared pan. Sprinkle generously with the cinnamon-sugar mixture. Cover with remaining cake batter. Bake at 400ºF for 8 minutes. Lower heat to 350ºF and bake for an additional 40 minutes. (Option: After cooling the cake, sprinkle with powdered sugar and drizzle with melted caramel.)