Tarte au Citron

Step 1

In a large bowl, whisk together 1.5 cups all-purpose flour and 0.25 teaspoon kosher salt. Add 0.5 cup cold unsalted butter cubed into 0.5-inch pieces — the cold butter creates steam pockets for a flaky crust. Using a pastry cutter or your fingertips, work the butter into the flour using a rubbing motion until the mixture resembles coarse breadcrumbs with some pea-sized butter pieces remaining.

Step 2

In a small bowl, whisk together 1 large egg yolk and 2 tablespoons ice water. Pour this mixture into the flour and use a fork to gently toss until just-combined shaggy pieces form. Do not overwork — you want visible butter pieces to remain for layers.

Step 3

Turn the dough onto a lightly floured surface and gather it into a disk without kneading. Wrap tightly in plastic and refrigerate for at least 30 minutes — this resting time relaxes the gluten so the dough doesn't shrink during baking.

Step 4

Preheat your oven to 375°F (190°C). Line a 9-inch tart pan with a removable bottom by rolling out the chilled dough on a floured surface to a 1/8-inch thickness — about 11 inches in diameter. Transfer it to the pan, press gently into the corners, and trim any overhang with a knife. Prick the bottom several times with a fork to prevent bubbling.

Step 5

Line the tart shell with parchment paper and fill with pie weights or dried beans — the weights prevent the pastry from puffing and shrinking. Blind-bake for 12-15 minutes until the edges are pale golden and set. You should see the sides lift slightly and turn light brown. Remove the weights and parchment, then bake for another 2-3 minutes until the bottom is dry and barely golden.

Step 6

Remove the tart shell from the oven and let cool for 5 minutes while you prepare the filling. Keep the oven at 375°F — you'll bake the finished tart at this temperature.

Step 7

Zest 4 large lemons on a microplane into a small bowl — you should have about 2 tablespoons of finely grated zest with no bitter white pith. Halve the lemons and juice them into a separate bowl, straining out seeds; you need about 0.75 cup fresh juice.

Step 8

In a heatproof bowl, whisk together 4 large eggs and 1 cup granulated sugar until pale and thick, about 3 minutes of whisking — this incorporates air and helps prevent the filling from curdling. Add the lemon zest, lemon juice, 0.25 cup softened unsalted butter, and 0.5 tablespoon cornstarch. Whisk until completely smooth.

Step 9

Set the bowl over a pot of gently simmering water (do not let the bottom touch the water), creating a double boiler. Cook, stirring constantly with a silicone spatula, for 8-10 minutes until the mixture reaches 160°F on an instant-read thermometer — this temperature pasteurizes the eggs safely. The curd should be thick, pale yellow, and steam slightly. Once it coats the back of a spoon with no drips, it's ready.

Step 10

Pour the hot lemon curd into the pre-baked tart shell, spreading it evenly with an offset spatula. Bake at 375°F for 8-10 minutes until the filling is just set but still slightly jiggly in the very center — it will continue to set as it cools. The top should look matte and smooth, not liquid.

Step 11

Remove from the oven and let the tart cool on a wire rack for at least 1 hour at room temperature — the filling sets and the flavors develop as it cools. You can also refrigerate for up to 4 hours and serve chilled or at room temperature.

Step 12

Just before serving, dust the top lightly with 1 tablespoon powdered sugar using a fine-mesh sieve for even coverage. Unmold the tart by pressing up on the removable bottom, then slice with a long thin knife dipped in hot water and wiped clean between cuts — the heat prevents the curd from tearing.