Lemon and Lime Meringue Tart

Sift all-purpose flour, powdered sugar, and fine sea salt into a heatproof glass bowl to remove lumps.

Rub the cold cubed unsalted butter into the dry ingredients using your fingertips until the mixture resembles coarse sand with pea-sized bits.

Add the chilled egg yolk and ice-cold water, mixing gently with a fork until the dough barely clumps together.

Shape the dough into a flat circular disc, wrap tightly in plastic wrap, and chill in the refrigerator for 45 minutes.

Roll out the chilled dough on a lightly floured surface using a rolling pin into a 30 cm circle roughly 3 mm thick.

Transfer the rolled dough into the 23cm fluted tart pan with removable base, pressing gently into the corners and fluted sides, then trim away excess overhang.

Dock the entire base of the pastry shell with a dinner fork to vent trapped air during baking.

Preheat the oven to 190°C (375°F).

Line the pastry shell with crumpled parchment paper, fill to the top with pie weights, and bake at 190°C (375°F) for 15 minutes.

Remove the parchment paper and pie weights, reduce oven temperature to 175°C (350°F), and bake uncovered for 10 minutes until the base is dry and golden.

Transfer the tart pan onto a wire cooling rack and allow the crust to cool completely for 20 minutes.

Grate the outer zest of the lemons and limes using a microplane grater, avoiding the bitter white pith.

Halve and squeeze the citrus using a citrus juicer, measuring out 100 ml of fresh lemon juice and 50 ml of fresh lime juice.

In a medium saucepan off the heat, whisk together the granulated sugar, cornstarch, and fine sea salt until uniform, then vigorously whisk in whole eggs, egg yolks, lemon juice, lime juice, and citrus zests.

Set the saucepan over medium-low heat and cook, whisking constantly and scraping the edges of the pan, until the curd comes to a boil and reaches 82°C (180°F) on an instant-read digital thermometer to activate the starch and cook the eggs safely above 71°C (160°F).

Pour the hot curd through a fine mesh sieve into a heatproof glass bowl, pressing with a silicone spatula to remove any accidental egg solids.

Add the softened cubed unsalted butter to the warm strained curd a few pieces at a time, whisking continuously until fully melted and glossy.

Pour the warm emulsified citrus curd directly into the pre-baked shortcrust pastry shell, smoothing the surface with a silicone spatula.

Chill the filled tart uncovered in the refrigerator for 60 minutes until the curd sets firmly.

Place egg whites, granulated sugar, cream of tartar, and fine sea salt in a clean heatproof glass bowl over a medium saucepan of gently simmering water, whisking constantly until the sugar completely dissolves and the mixture registers 71°C (160°F) on an instant-read digital thermometer for safe egg consumption.

Transfer the warm egg white mixture to the bowl of a stand mixer fitted with the whisk attachment, add pure vanilla extract, and whip on high speed for 8 minutes until stiff, glossy peaks form and the bowl feels cool to the touch.

Transfer the whipped meringue into a pastry piping bag fitted with a star nozzle and pipe decorative rosettes and peaks across the top of the chilled tart, sealing all the way to the pastry crust edges.

Lightly brown the exterior of the meringue with a culinary kitchen torch held 8 cm away, sweeping continuously until the ridges are caramelized and golden brown.

Wipe a sharp chef's knife with warm water between cuts, slice the tart into 8 equal wedges, and serve.