Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 10 inch Bundt pan. In a medium bowl, mix the flour, baking powder and baking soda together and set aside. In a separate small bowl, combine 1/2 cup sugar, cinnamon, and nuts. Set aside.
In a large bowl, cream butter and 2 cups white sugar until light and fluffy. Add eggs, sour cream, and vanilla extract. Add flour mixture and beat until well combined.
Pour half of batter into Bundt pan. Sprinkle half of the nut mixture on top of batter in pan. Add remaining batter, and sprinkle with the last of the nut mixture.
Bake at 350 degrees F (175 degrees C) for 45 to 60 minutes, or until a toothpick inserted into cake comes out clean.