Mix flour, powdered sugar, and salt. Cut cold butter into 1/4"e slices and cut into flour mixture. Mix to a fine crumb stage. Press evenly into the bottom of a greased 9x13"e pan. Bake 20 minutes at 325F. Beat eggs and add remaining ingredients, except powdered sugar. Mix well.
Pour lemon mixture over hot crust, increase heat to 350F, and bake another 20 minutes until golden. Sift powdered sugar onto bars while hot. Cool in pan on wire rack. Cut into small squares and then in half to make diamond shaped bars. Cover and store in refrigerator, serve chilled.