Preheat oven to 350. Grease and flour 9 to 10 inch tube pan. In a small bowl, combine 2/3 cup sugar, walnuts and cinnamon. In medium bowl, combine flour, baking powder, baking soda and salt. In large bowl, mix at low speed, beat butter and 1 3/4 cups sugar until blended increase to high speed and beat until light and fluffy, about 2 mins. Reduce to low, add eggs, one at a time, beating well after each egg and add vanilla. Alternately add flour mixture and sour cream, starting and ending with flour mixture, beat until smooth. Spoon 1/3 of batter into pan. Sprinkle with half of nut mixture, then top with remaining batter and sprinkle with the rest of nut mixture. Bake until toothpick comes out clean, about 1 hour 20 minutes. Cool in pan on wire rack for 10 minutes. Run thin knife around cake to loosen from sides of pan. Invert cake onto plate. Turn cake, nut mixture side up and cool completely. Enjoy!