Cream butter, sugar and vanilla until light and fluffy. Add eggs one at a time, beating well after each addition. Combine flour, baking powder and salt. Stir one third of the flour mixture into creamed mixture. Stir until blended. Add one-half the sour cream and blend. Repeat procedure, ending with dry ingredients. Pour one third of the batter into a greased bundt pan. Combine pecans, sugar and cinnamon. Sprinkle one third of mixture onto the batter. Repeat with remaining batter. Bake at 350 degrees F for 55 minutes. Cool one hour in pan. Invert.