Preheat oven to 375 degrees. Grease a 9 X 13 inch baking pan.
Combine the flour, 2/3 cup powdered sugar, and butter. Pat dough into prepared pan.
Bake 20 minutes in preheated oven, until lightly golden brown. While crust is baking, whisk together the eggs, granulated sugar, 3 Tbsp. flour, and lemon juice until frothy. Pour this mixture over the hot crust.
Return to oven for an additional 20-25 minutes, or until light golden brown.
Cool in the pan, on a wire rack.
Dust with powdered sugar, if desired. Cut into squares.