Preheat oven to 350 degrees. Mix together butter, powdered sugar and flour until well blended. Press mixture into the bottom of a 9x13-inch glass baking dish. Bake for 20 minutes.
Sift together sugar, flour and baking powder into a mixing bowl. Add eggs, lemon juice and lemon rind. Beat by hand or with electric mixer until well blended. Pour mixture over crust and bake for 25 minutes.
Allow bars to cool, then dust with powdered sugar and cut into squares.