Heat oven to 350ºF.
In a medium bowl, mix flour, butter and powdered sugar. Press into an ungreased square pan, 8x8x2 or 9x9x2 inches, building the edges up 1/2-inch.
Bake the crust for 20 minutes.
In the same bowl, beat the granulated sugar with a hand mixer, with lemon peel, lemon juice, baking powder, salt and eggs, for about 3 minutes, or until light and fluffy. Pour the mixture over the hot crust.
Bake 25 to 30 minutes.
Cool; dust with powdered sugar. Cut into 1 1/2-inch squares.