Sour Cream Apple Squares

1 (18.25 ounce) box yellow cake mix
1/2 cup butter or margarine, softened
1/4 cup firmly packed brown sugar
1 teaspoon cinnamon
2 apples, pared and thinly sliced
1 cup sour cream
1 egg

Heat oven to 350 degrees F.

Combine dry cake mix and butter; mix until crumbly. Reserve two-thirds for topping.

Add brown sugar and cinnamon to reserved topping mix; blend well and set aside.

Press remaining mixture onto the bottom of ungreased 13 x 9-inch pan. Arrange apple slices over base.

Blend sour cream and egg; spread evenly over apples. Sprinkle reserved topping mix over all. Bake for 25 to 30 minutes.

Serve warm. Refrigerate leftovers.