In bowl combine flour, sugar and butter. Pat into 9X13 pan. Bake for 20 minutes in a 350F oven. While it is baking, whisk together eggs, 3 Tb flour, sugar and lemon juice. Pour over crust while crust is still hot. Bake for an additional 20-25 minutes, or until top is golden brown. Cool on a wire rack and dust with additional powdered sugar.