To make the crust: Preheat the oven to 325°F. Combine the flour and confectioners' sugar in the bowl of a stand mixer fitted with the paddle attachment and beat on low speed until mixed. Add the butter and continue to mix until the butter is the size of small peas, about 30 seconds. The mixture will be very dry. Gently press the mixture evenly onto the bottom of a 9-by-13-inch baking pan.

Bake until golden brown, 20 to 25 minutes. Let cool to room temperature. Reduce the oven temperature to 300°F.

To make the filling: In a large bowl, whisk together the eggs and granulated sugar until smooth. Stir in the lemon juice and then the flour. Pour the filling on top of the crust.

Bake until the lemon filling is set, about 40 minutes. Let cool to room temperature and then put in the refrigerator for 1 hour or keep at room temperature for 3 hours before cutting. Cut into squares measuring about 2 1/4 inches and dust the tops with the confectioners' sugar.

Planning Ahead: The squares maybe made a day in advance, covered, and refrigerated. Bring to room temperature before serving.