Preheat oven to 375º F. Grease a 6 x 12-inch baking pan. In the large bowl of a mixer, cream sugar and butter. In another large bowl stir together flour, baking powder, baking soda and salt. In a small bowl, blend together eggs, sour cream and vanilla. Alternately add the dry ingredients and the sour cream mixture to the butter mixture, mixing batter just until blended. Pour half the batter into the prepared pan and spread evenly. Sprinkle with 2 tablespoons of the Cinnamon Sugar. Spoon on the remaining batter and spread evenly. Scatter blueberries and walnuts over top of batter and sprinkle with remaining Cinnamon Sugar. Bake for 40 to 45 minutes or until toothpick inserted near center comes out clean. Serve warm, with vanilla ice cream, if desired.

Cinnamon Sugar: In a small bowl stir together 5 tablespoons sugar and 1 tablespoon cinnamon.