Lemon Custard Squares

Read through the recipe and gather the equipment. Use the ingredient lines to prepare and measure everything, and let the butter soften on the counter. Do not taste the raw crust dough or the raw filling; they contain raw flour, and the filling raw egg. Everything is measured and the butter is soft.

Heat the oven to 350°F with a rack in the middle. The oven is heating.

Mix about 2 cups all-purpose flour, about 1 cup butter and about 1/2 cup sugar in a medium bowl until it forms a crumbly dough that holds together when you pinch it. Press it evenly over the bottom of the 9-by-13-inch baking pan. The crust is pressed into an even layer.

Bake the crust on a rack in the middle at 350°F until it is firm and golden at the edges, about 15 minutes.

Whisk about 1 1/2 cups sugar and about 1/4 cup all-purpose flour in the second bowl, then whisk in 4 whole large eggs and the lemon juice until the filling is smooth.

Pour the filling over the hot crust and bake on a rack in the middle at 350°F until the filling is set and no longer jiggles in the center, about 20 minutes. An instant-read thermometer in the center of the filling reads 160°F (71°C).

Cool the pan on the wire rack until it is at room temperature all the way through and the filling is firm, about 1 to 2 hours.

Cut into even squares with a sharp knife, wiping the blade between cuts, to make 24 servings. Taste a corner piece. Aim for bright, tart lemon balanced by sweetness, on a crisp base. If it tastes too sharp, chill the squares before serving, which softens the tartness. Refrigerate leftovers, covered. The squares are cut and ready to serve.