Use a microplane to get the lemon zest grated as thinly as possible—or shave it off with the large holes of a box grater and then mince it on a cutting board until you have the smallest, thinnest threads.

16 tablespoons (2 sticks) cool unsalted butter, cut into small cubes, plus additional for greasing the pan

11⁄2 cups plus 2 tablespoons all-purpose fl our

1⁄3 cup plus 1 tablespoon confectioners’ sugar

1⁄4 teaspoon salt

11⁄2 cups granulated sugar

3 large eggs plus 1 large egg yolk, at room temperature

6 tablespoons lemon juice

1 tablespoon finely grated lemon Zest

• Position the rack in the center of the oven; preheat the oven to 350°F. Lightly butter a 9-inch baking pan; set it aside.
• Mix 11⁄2 cups fl our, 1⁄3 cup confectioners’ sugar, and the salt in a large bowl. Add the chunks of butter and cut them into the fl our mixture with a pastry cutter or a fork until the mixture is a little coarser than dry oat bran.
• Press this mixture evenly across the bottom of the prepared pan, making sure there are no holes and compacting the mixture somewhat to form a cookielike crust.
• Bake until lightly browned at the edges, about 25 minutes. Remove from the oven and set aside on a wire rack.
• Without delay, beat the granulated sugar, eggs, and egg yolk in a medium bowl with an electric mixer at medium speed until pale yellow and quite thick, like a thin sabayon, about 3 minutes. Beat in the lemon juice and lemon zest, scrape down the sides of the bowl with a rubber spatula, and beat in the remaining 2 tablespoons fl our. Pour this mixture evenly over the hot crust.
• Return the pan to the oven and bake until the fi lling is set (it should jiggle a bit when shaken, but there should be no liquid in the mixture), about 25 minutes.
• To cool: Transfer to a wire rack and cool completely, about 1 hour. Sprinkle the remaining 1 tablespoon confectioners’ sugar over the pan, then cut the cookies into 16 squares (making four cuts each way in the pan).
• To store: The bars can be kept in a sealed container between sheets of wax paper for up to 3 days.
• Makes 16 bar cookies

Use a microplane to get the lemon zest grated as thinly as possible—or shave it off with the large holes of a box grater and then mince it on a cutting board until you have the smallest, thinnest threads. Makes 16 bar cookies
• 16 tablespoons (2 sticks) cool unsalted butter, cut into small cubes, plus additional for greasing the pan
• 11⁄2 cups plus 2 tablespoons all-purpose fl our
• 1⁄3 cup plus 1 tablespoon confectioners’ sugar
• 1⁄4 teaspoon salt
• 11⁄2 cups granulated sugar
• 3 large eggs plus 1 large egg yolk, at room temperature
• 6 tablespoons lemon juice
• 1 tablespoon fi nely grated lemon zest

• Position the rack in the center of the oven; preheat the oven to 350°F. Lightly butter a 9-inch baking pan; set it aside.
• Mix 11⁄2 cups fl our, 1⁄3 cup confectioners’ sugar, and the salt in a large bowl. Add the chunks of butter and cut them into the fl our mixture with a pastry cutter or a fork until the mixture is a little coarser than dry oat bran.
• Press this mixture evenly across the bottom of the prepared pan, making sure there are no holes and compacting the mixture somewhat to form a cookielike crust.
• Bake until lightly browned at the edges, about 25 minutes. Remove from the oven and set aside on a wire rack.
• Without delay, beat the granulated sugar, eggs, and egg yolk in a medium bowl with an electric mixer at medium speed until pale yellow and quite thick, like a thin sabayon, about 3 minutes. Beat in the lemon juice and lemon zest, scrape down the sides of the bowl with a rubber spatula, and beat in the remaining 2 tablespoons fl our. Pour this mixture evenly over the hot crust.
• Return the pan to the oven and bake until the fi lling is set (it should jiggle a bit when shaken, but there should be no liquid in the mixture), about 25 minutes.
• To cool: Transfer to a wire rack and cool completely, about 1 hour. Sprinkle the remaining 1 tablespoon confectioners’ sugar over the pan, then cut the cookies into 16 squares (making four cuts each way in the pan).
• To store: The bars can be kept in a sealed container between sheets of wax paper for up to 3 days

Variations:
• Lime Bars: Substitute lime juice for the lemon juice; substitute 2 teaspoons fi nely grated lime zest for the lemon zest.
• Lime Coconut Bars: Substitute lime juice for the lemon juice; substitute 1 tablespoon fi nely ground sweetened coconut for the lemon zest. When they’re fully cooled, dust the top of the bars with 1 tablespoon fi nely ground sweetened coconut.
• Orange Bars: Substitute thawed orange juice concentrate for the lemon juice; substitute orange zest for the lemon zest but also add 1 teaspoon lemon juice.