In a small bowl, combine the powdered sugar and flour.
Cut in the butter until it's the size of small peas.
Press this mixture evenly in the bottom of a 9 x 13-inch pan.
Bake 15 minutes.
Meanwhile, beat together eggs, sugar, baking powder, salt, lemon peel and lemon juice until fluffy.
Pour this mixture over the hot crust.
Bake 20 to 25 minutes longer, or until no imprint remains when touched lightly in the center.
Sift powdered sugar over the top.
Cool in the pan.
Refrigerate for four hours or overnight before cutting (yeah, like that will happen).
Store in the refrigerator.
2002 Desolina (Elizabeth Finan) gave me this recipe when Bea was one, and said she'd love it. She did! October 14, 2011 Made a batch with orange instead of lemon, and you almost couldn't tell the difference.