Grease and flour an 8x4x2-inch loaf pan; set pan aside.
In a large bowl, beat sugar, sour cream, egg, and vanilla until combined.
Stir together flour, baking powder, baking soda, and salt. Stir into sugar mixture.
Fold in walnuts. Pour batter into prepared pan.
Bake in a 325 degree F oven for about 65 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes on a wire rack. Remove from pan; cool thoroughly on a wire rack. Makes l loaf.