Step 1

Freeze the butter. Cube 1 stick unsalted butter and place in a small bowl. Freeze for 5 minutes while you prepare the wet and dry ingredients.

Step 2

Mix the wet and dry ingredients. Place 1 large egg yolk, 1 tablespoon heavy cream, and 1 teaspoon vanilla extract in a small bowl and whisk with a fork to combine. Place 1 1/4 cups all-purpose flour, 2/3 cup powdered sugar, and 1/2 teaspoon kosher salt in a food processor fitted with the blade attachment. Pulse a few times to combine.

Step 3

Mix in the butter. Scatter the cold pieces of butter over the flour mixture. Pulse until the mixture is like coarse sand, about 15 (1-second) pulses.

Step 4

Mix the dough. With the motor running, pour the egg mixture through the tube and process until big clumps of dough form, 20 to 30 seconds.

Step 5

Roll out and freeze the dough. Transfer the dough to a sheet of parchment paper and gather into a smooth disc. Top with a second sheet of parchment paper and roll the dough into an 11-inch round that’s a little thicker than 1/8-inch. Slide the dough (still in the parchment) onto a baking sheet and freeze for 5 minutes.

Step 6

Line the tart pan and freeze. Uncover the dough (reserve one of the parchment sheets) and transfer the dough into a 9-inch round tart pan with removable bottom. Gently ease and then press it into the sides and onto the bottom of the pan, making sure it fits snugly into the corners. Trim off any excess dough by running the rolling pin over the top of the pan. (If needed, press the dough scraps into any gaps in the crust that need patching.) Freeze the tart shell 30 minutes. Meanwhile, prepare the lemon zest and juice and heat the oven.

Step 7

Prepare the lemons and heat the oven. Finely grate the zest of 4 to 5 medium lemons until you have 1/4 cup loosely packed. Halve and juice the lemons until you have 2/3 cup. Place the zest and juice in a large heatproof (not aluminum) bowl. Arrange a rack in the middle of the oven and heat the oven to 375ºF.

Step 8

Par bake the crust. When the crust is ready, place on a baking sheet. Press the reserved sheet of parchment paper onto the crust and fill with pie weights. Bake until set, about 30 minutes.

Step 9

Uncover and finish par-baking the crust. Remove the weights and parchment. Bake until just starting to turn light golden brown at the edges, about 5 minutes. Place the baking sheet on a wire rack while making the filling (the filling needs to go into a warm crust) and keep the oven at 375ºF.

Step 10

Prepare a double boiler. Fill a large saucepan with about 1 1/2 inches water and bring to a simmer over medium heat. Fit a fine-mesh strainer over a medium bowl.

Step 11

Prepare the filling ingredients. Add 7 large egg yolks, 2 large eggs, 1 cup granulated sugar, and 1/4 teaspoon kosher salt to the lemon zest and juice and whisk to combine. Cut 4 tablespoons unsalted butter into 4 pieces and add to the lemon mixture.

Step 12

Cook the lemon filling. Place the bowl onto the saucepan of simmering water and cook, stirring constantly with a heatproof spatula, until the mixture thickens slightly to the consistency of cold heavy cream and registers 170ºF on an instant-read thermometer, 7 to 8 minutes. Remove from the heat (some small lumps are okay).

Step 13

Add the cream and strain the lemon filling. Stir in 3 tablespoons cold heavy cream. Pour the mixture through the fine-mesh strainer and discard the contents of the strainer (make sure to scrape anything clinging to the underside of the strainer into the bowl).

Step 14

Bake the tart. Pour the filling into the warm crust. If there are any bubbles in the filling, gently pick up the pan and tap it against the counter. Bake until the center jiggles slightly when gently shaken but the rest of the filling is set, 10 to 15 minutes.

Step 15

Cool the tart. Place the baking sheet on a wire rack and let the tart cool completely, about 1 hour. Remove the outer ring and garnish with powdered sugar or whipped cream and candied lemon peel. Cut into slices and serve.