Shortbread, Lemon, Meringue Recipe

Prepare oven and pan

Preheat the oven to 350°F (175°C). Lightly butter or line an 9x9-inch (23x23 cm) square baking pan with parchment, leaving an overhang for easy removal.

Make dough

In a large bowl whisk together the all-purpose flour, powdered sugar, and fine sea salt. Add the cold cubed unsalted butter and the vanilla extract. Using a pastry cutter, two forks, or your fingertips, cut the butter into the flour until the mixture resembles coarse crumbs with some pea-sized pieces remaining.

Press and blind bake

Press the mixture evenly into the prepared pan, pressing firmly to create a compact, even layer. Prick the surface lightly with a fork to prevent bubbling. Bake for 18–22 minutes, or until the edges are just beginning to turn lightly golden. Remove from oven and set aside to cool slightly while you prepare the curd. Leave the oven on (see meringue finishing).

Combine and cook curd

In a medium heavy-bottomed saucepan, whisk together the egg yolks, whole egg, granulated sugar, lemon juice, and lemon zest until smooth. Place the pan over low–medium heat and cook, stirring constantly with a heatproof spatula, scraping the bottom and sides, until the mixture thickens enough to coat the spatula and reaches about 170–175°F (77–80°C). This usually takes 6–8 minutes. Do not let it boil.

Finish the curd

Remove the pan from the heat and immediately whisk in the cold cubed butter a few pieces at a time until fully incorporated and the curd is glossy and smooth. If there are any small curdled bits, strain the curd through a fine-mesh sieve into a bowl. Let the curd cool slightly, then pour it evenly over the warm shortbread crust. Smooth the top with a spatula. Chill in the refrigerator for 20–30 minutes to firm slightly while you make the meringue.

Prepare egg whites

Ensure your mixing bowl and whisk or beaters are clean and free of grease. In a large mixing bowl, add the egg whites and cream of tartar. Begin beating on medium speed until foamy.

Add sugar and finish meringue

Gradually add the granulated sugar, about 1–2 tablespoons at a time, while increasing the mixer speed to high. Beat until glossy, stiff peaks form and the sugar is dissolved (rub a small amount between your fingers to check for grittiness). Beat in the vanilla extract at the end.

Top and bake

Remove the chilled curd-topped shortbread from the refrigerator. Spoon or pipe the meringue over the lemon curd, making peaks if desired to get attractive browning. Option A: For a soft marshmallow meringue, bake at 350°F (175°C) for 8–10 minutes, just until the meringue is lightly browned. Option B: For a deeper toasted top, use a kitchen torch to brown the peaks after baking or reduce oven to 425°F (220°C) and bake 3–5 minutes while watching closely. Let the finished bars cool to room temperature, then chill 30 minutes to set the layers.

Garnish and serve

Sprinkle the finely grated lemon zest over the meringue just before serving for bright aroma. Using the parchment overhang, lift the whole slab from the pan and cut into 9 or 12 bars with a sharp knife (wipe the knife between cuts for clean edges).