Lemon Squares II

Preheat oven to 350 degrees F (180 degrees C). Mix flour, butter and powdered sugar thoroughly. Press evenly into an ungreased 8 x 8 x 2 inch or 9 x 9 x 2 inch square pan. Make a little rim up the edges to hold in the filling. A quarter inch or so will do it. Bake 20 minutes. Beat remaining ingredients about 3 minutes of until light and fluffy. Pour over the hot crust, spreading it out evenly. Bake about 25 minutes longer or until no imprint remains when touched lightly in the center. Remove from oven, sprinkle the extra powdered sugar on the top, if you like. Cool, cut into squares.