In a large bowl beat together sugar, sour cream, eggs and vanilla on low speed of an aelectric mixter till combined then beat on medium speed 2 minutes.
Stir together flour, baking powder, soda and salt, add to sour cream mixture, beating on low speed till combined. Stir in apple and 1/2 c the pecans. Turn into a greased 9 x 5 x 3 inch loaf pan. Sprinkle with remaining chopped pecans; press lightly into batter.