To make crust: Cream the butter and sugar in a bowl of an electric mixer fitted with the paddle attachment until light and creamy. Add in flour and salt and mix on low until just combined. Dump the dough onto a well-floured board and gather into a ball. Flatten the dough with floured hands and press it into a 9 by 13 by 2-inch baking sheet, building up a 1/2-inch edge on all sides. Chill for at least 30 minutes. Bake crust for 15 to 20 minutes, until very lightly browned. Let cool on a wire rack. Leave the oven on.
To make filling: In a bowl, whisk the eggs, sugar, lemon zest, lemon juice, and flour. Pour mixture over crust and bake for about 30 to 35 minutes or until the filling is set. Let cool to room temperature.
Dust with confectioner sugar and cut to squares to preferred size.