Lemon squares are a favorite in the American household, but they are so often ruined by soggy crusts and grainy, muddled curds. This America's Test Kitchen recipe yields a lemon square with a mouthwateringly tart, lusciously smooth curd coupled with a sturdy, buttery crust.
We chose honey to sweeten both components, both for its subtle flavor and its smooth texture that makes it perfect for liquid mixtures. For the crust, we chose a simple press-in crust. By mixing softened butter and flour to a sandy texture, we produced a crust with a texture between short and flaky. A small amount of honey provided sweetness, while a bit of water hydrated the dough just enough to make it workable. For the curd, we started with traditional flour-thickened mixtures that were cooked in the oven. But these versions were consistently grainy, pale, and muted in lemon flavor. Without the aid of granulated sugar to disperse the flour in the mixture, clumps formed in the curd. Moreover, the curd’s appearance was unreasonably sensitive to minute variations in baking time and temperature: If the curd was cooked 1 minute too long or the oven was running a bit too hot, the result was an unsightly cracked surface. We opted instead for the more foolproof method of starting the curd on the stovetop and then finishing it in the oven. Rather than rely on flour for thickening power, this method took advantage of the honey’s viscosity to produce a smooth, velvety curd. A generous number of egg yolks produced a vibrant yellow color and rich flavor, and also provided great emulsifying power. To boost the lemon flavor, we introduced a hefty amount of lemon zest. Finishing the curd with a small amount of butter and cream gave the curd a silky consistency and good dimension. Finally, straining the curd ensured an irresistibly smooth texture. When eaten together with the buttery crust, our lemon squares had a welcome textural contrast and enticing pucker perfect for lemon lovers.
Makes 16 bars
To avoid air bubbles in the curd, stir in the cream with a spatula.
1 cup (5 ounces) all-purpose flour
¼ teaspoon salt
6 tablespoons unsalted butter, cut into 6 pieces and softened
2 teaspoons water
1 teaspoon honey
2 large eggs plus 7 large yolks
½ cup honey
¼ cup grated lemon zest plus
⅔ cup juice (4 lemons)
⅛ teaspoon salt
4 tablespoons unsalted butter, cut into 4 pieces
3 tablespoons heavy cream
1. For the crust: Adjust oven rack to middle position and heat oven to 350 degrees. Make foil sling for 8-inch square baking pan by folding 2 long sheets of aluminum foil so each is 8 inches wide. Lay sheets of foil in pan perpendicular to each other, with extra foil hanging over edges of pan. Push foil into corners and up sides of pan, smoothing foil flush to pan. Grease foil.
2. Using stand mixer fitted with paddle, mix flour and salt on low speed until combined, about 30 seconds. Add butter, 1 piece at a time, and mix until only pea-size pieces remain, about 1 minute. Add water and honey and continue to mix until mixture begins to clump and resembles wet sand, about 30 seconds.
3. Transfer mixture to prepared pan and press into even layer with bottom of dry measuring cup. Bake crust until golden brown, 20 to 25 minutes, rotating pan halfway through baking.
4. For the lemon curd: Meanwhile, whisk eggs and yolks, honey, lemon zest and juice, and salt together in medium saucepan until smooth. Cook over medium-low heat, stirring constantly with rubber spatula, until mixture thickens slightly and registers 165 degrees, about 5 to 7 minutes. Off heat, whisk in butter until melted. Strain lemon curd through fine-mesh strainer into bowl, then gently stir in cream with rubber spatula.
5. Pour warm lemon curd over hot crust. Bake until filling is shiny and opaque and center jiggles slightly when shaken, 10 to 12 minutes, rotating pan halfway through baking. Let bars cool completely in pan, about 2 hours. Using foil overhang, lift bars from pan and transfer to cutting board. Cut into squares and serve.
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