Preheat oven to 350 degrees F. Line a 13x9x2-inch baking pan with foil, leaving about 1 inch of foil extending over the ends. In a large bowl, stir together the 2 cups flour and the 1/2 cup powdered sugar. Add butter and beat with an electric mixer on low to medium speed just until mixture begins to cling together. Press into the bottom of prepared baking pan. Bake about 25 minutes or until lightly browned.
In a medium bowl, beat eggs with a whisk; whisk in granulated sugar and lemon juice until well mixed. Whisk in the 1/4 cup flour and the lemon peel. Pour over baked crust.
Bake about 20 minutes more or until edges begin to brown and center is set. Cool in pan on a wire rack. Remove bars from pan, using the overlapping foil to lift from pan. Sift additional powdered sugar over top. Cut into bars or into 21 3/4-inch diamonds. Store, covered, in refrigerator.