Preheat oven to 350 degrees F. Lightly grease and flour a 13 x 9-inch baking pan. In large bowl,beat margarine until creamy. Gradually add sugars and beat until light and fluffy. Add egg and egg whites and beat until smooth. Add peanut butter and mix until smooth. Combine flour, baking powder, baking soda and salt. Add dry ingredients to peanut butter mixture alternately with buttermilk until blended. Stir in apples just until blended. Do not overmix cake batter. Pour cake mixture into prepared pan. Sprinkle peanut topping evenly over cake batter.

Bake for about 50 minutes or until toothpick comes out clean.

Peanut Topping
In a bowl, cut together the sugar, flour and margarine until crumbly. Stir in peanuts.

Photo and Recipe Courtesy of The National Peanut Board.