In a bowl whisk together eggs and granulated sugar until combined well and stir in lemon juice and flour.
Pour lemon mixture over hot shortbread. Reduce oven temperature to 300°F. and bake confection in middle of oven until set, about 30 minutes. Cool completely in pan and cut into 24 bars. Bar cookies keep, covered and chilled, 3 days. Sift confectioners' sugar over bars before serving.