Cream together 1/2 pound of butter, 1/2 cup granulated sugar, and 2 cups of flour. When the mixture is crumbly press into a 13 x 9 inch baking dish. Press dough out evenly so that it has a uniform height through out the pan. Bake for approximately 15 minutes, and remove from the oven.
In a bowl mix together 6 eggs, 3 cups granulated sugar, 1 cup lemon juice, 1 cup flour, vanilla, and salt. Mix until the filling is uniform in texture, and pour over the cooked shortbread cookie crust. Bake for an additional 30 to 35 minutes. Allow this to cool to room temperature before dusting with powdered sugar. Be sure to refrigerate these cookies when not being served.