These lemon squares are sure to be a welcome treat with their tender shortbread crust and sweet-tart lemon curd filling.

Lemon Squares

Crust:
8 ounces (2 sticks) unsalted butter, chilled and cut into 1/2-inch pieces
1/2 cup confectioners' (powdered) sugar
1/4 teaspoon salt
1 cup all-purpose flour
1 cup cake flour
Optional: 1/2 cup sliced almonds, toasted and finely chopped

Lemon Layer:
Zest of 3 large lemons, finely grated
1/3 cup all-purpose flour
4 large eggs
1 cup plus 1 tablespoon granulated sugar
2/3 cup fresh lemon juice, strained

1. Prepare a 9-inch baking pan by either spraying the bottom and sides generously with a non-stick baking spray or brush with surface with softened butter, dusting it lightly with flour.
2. To assemble the crust, use a food processor fitted with the metal blade attachment. Combine the confectioners' sugar, salt, all-purpose and cake flour altogether pulsing the machine to mix well. Scatter the chilled butter pieces over the dry ingredients and process mixture briefly, pulsing machine until dough just begins to come together. If adding nuts do so towards the very end of processing. With lightly floured fingers remove dough from bowl and press into an even layer over the bottom of the prepared pan. Chill briefly in freezer or refrigerator until it's firm, about 15 to 20 minutes.
3. Preheat oven to 350°F (175°C) and bake crust 15 to 20 minutes or until the surface appears a light golden brown all-over. After crust is baked reduce oven temperature to 300°F (150°C).
4. While crust is baking prepare lemon custard layer. In a large mixing bowl, grate the zest of 3 large lemons, which have been washed and dried, careful to remove only the fragrant yellow skin, not the bitter white pith which lies underneath it. Add zest to the flour, eggs, and sugar whisking well by hand. In a steady stream, add the lemon juice, strained of all seeds and pulp, whisk until incorporated (noting you should not whisk too vigorous creating an undesirable foam and froth across the surface).
5. To bake, gently pour the custard over the warm crust, return to 300°F (150°C) oven and bake an additional 20 to 25 minutes, carefully rotating the pan 2 to 3 times while it bakes. Lemon layer is cooked when the custard is just barely set all over, with the center remaining slightly loose but not watery. Custard will continue to bake a few minutes longer after it has been removed from the oven. Cool thoroughly and sprinkle generously with confectioners' sugar shortly before serving. Store well wrapped up to 3 days.

Makes 12 bars.