Heat oven to 350°°

Mix flour, butter, and powdered sugar.

Press in ungreased baking pan, 8X8X2 inches, building up 1/2 inch edges.

Bake 20 minutes

Beat remaining ingredients until light and fluffy, about 3 minutes

Pour over baked layer.

Bake until no indentation remains when touched in the center, about 25 minutes

Let Cool

Cut into 1-inch squares

° if using self-rising flour, omit baking powder and salt