Mix butter, confectioners' sugar, flour, and salt. Pat in a greased 10"x13" pan. Bake at 350 for 20 minutes.
(TIP FROM SANDY - I always had trouble with the crust sticking after all the baking even when I greased the pan really well. Recently, I've been greasing the pan and then arranging parchment paper in it on the bottom and up the sides. I can lift the "cake" out and then cut into squares. Works well for me!)
LEMON TOPPING: Mix eggs, sugar, flour, lemon juice, and lemon rind; pour over crust. Bake at 350 for 20 - 25 minutes. Sprinkle sifted confectioners' sugar over top when you take the lemon squares from the oven. These are melt-in-your-mouth good!