Preheat oven to 350 degrees F. 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 degrees F. And bake 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.Shortbread Base:
Preheat oven to 350 degrees.
Cut butter into 1/2-inch pieces. In a food processor process all ingredients until mixture begins to form small lumps. Sprinkle mixture into a 13 by 9 by 2-inch baking pan and with a metal spatula press evenly onto bottom. Bake shortbread in middle of oven until golden, about 20 minutes. While shortbread is baking, prepare topping.