1/2 lb. (2 sticks) butter
1 c. sugar
3 eggs
2 1/2 c. all-purpose flour
2 tsp. baking powder
1 tsp. baking soda
1/2 tsp. salt
1 c. sour cream
1 1/2 c. coarsely chopped apple, peeled
1 1/2 c. coarsely chopped walnuts

Preheat oven to 350 degrees. Grease and flour a bundt pan (or a 10 inch tube pan). Put the butter in food processor and process for a few seconds. Add sugar and process until smooth. Add eggs and process until light and creamy. Put flour, baking powder, baking soda and salt in a bowl and stir with a fork to blend well. Slowly add the flour mixture and process until smooth. Add sour cream and process until well blended.

Transfer batter to a big bowl and carefully stir in the nuts and apple until well distributed. Spoon the batter into the pan. Bake for about 50 minutes or until a straw comes out clean when inserted into the center. Remove from oven and let rest for 5 minutes in the pan. Invert onto a rack and cool a little bit before slicing. Serve warm.