Cream shortening in a medium mixing bowl; gradually add sugar, beating well. Add eggs, one at a time, beating well after each addition. Add vanilla, stirring well.
Combine flour, baking powder, soda, and salt in a small bowl; stir well. Add flour mixture to creamed mixture alternately with sour cream, beginning and ending with flour mixture. Stir in apple.
Spoon batter into a greased 13- x 9- x 3-inch baking pan; sprinkle with topping. Bake at 350° for 35 to 40 minutes. Cut into squares, and serve warm.
Oxmoor House Homestyle Recipes