For the crust, combine flour and powdered sugar in a bowl. Cut in butter until mixture resembles coarse crumbs. Press into the bottom of an ungreased 9x13 inch baking pan.
Bake for 20 minutes, or until lightly golden.
While the crust is baking, prepare the filling. In a large bowl, whisk together eggs, sugar, and flour. Stir in lemon juice and zest.
Pour filling over the hot crust. Bake for 25-30 minutes, or until filling is set.
Let cool completely before cutting into squares. Dust with powdered sugar before serving.
Notes
For a tangier flavor, add an extra tablespoon of lemon juice.