Lemon Bars

Instructions

Make the crust: Heat the oven to 350°F and make a foil sling for an 8-inch square baking pan. Whisk together the flour, sugar, and salt in a bowl. Add the melted butter and stir until combined. Transfer to the prepared pan and press into an even layer over the entire bottom. Bake until dark golden brown, 19 to 24 minutes, rotating halfway through.

Make the filling: While the crust bakes, whisk together the sugar, flour, cream of tartar, and salt in a large bowl. Whisk in the eggs and yolks until no streaks remain, then whisk in the lemon zest and juice. Transfer to a saucepan and cook over medium-low heat, stirring constantly, until the mixture thickens and registers 160°F, 5 to 8 minutes. Off the heat, stir in the butter, then strain through a fine-mesh strainer into a bowl.

Bake & finish: Pour the filling over the hot crust and tilt the pan to spread evenly. Bake until the filling is set and barely jiggles when the pan is shaken, 8 to 12 minutes. Cool completely, at least 1½ hours. Use the foil overhang to lift the bars out of the pan and transfer to a cutting board. Cut into bars, wiping the knife clean between cuts. Dust with confectioners' sugar just before serving.