1/4 c. soft butter
1/2 c. sugar
1/2 tsp. vanilla
1 egg
1 c. flour
1/2 tsp. each baking soda and baking powder
1/4 tsp. salt
1/2 c. sour cream
1 lg. apple, finely diced (about 1 1/2 c.)
Nut topping

NUT TOPPING:

1/2 c. brown sugar
3/4 tsp. cinnamon
2 tbsp. soft butter

Mix topping ingredients until combined. Stir in 1/2 cup chopped walnuts. Set aside.

Cream butter and sugar. Beat in vanilla and egg. Mix dry ingredients and add to butter mixture alternately with sour cream. Mix just to blend. Fold in apples. Spread in 8" greased square baking pan. Sprinkle with nut topping. Bake at 350 degrees for 40 to 45 minutes, or until top is well browned and cake tests done with pick. Cut into squares and serve warm or at room temperature.