Preheat oven to 350 degrees.
In a medium bowl, mix flour, butter and confectioners sugar. Press evenly in ungreased 8x8x2 inches pan, building up 1/2-inch edges.
Bake 20 minutes.
In a mixing bowl, beat remaining filling ingredients until light and fluffy, about 3 minutes.
Pour over warm crust. Bake about 25 minutes or until center is firm. Cool. Sprinkle with confectioners sugar. Cut into 25 1-1/2-inch squares.