Combine the flour, sugar, and salt in a food processor. Pulse the food processor a few times to mix everything together. Add the butter and pulse a few more times, until the butter is cut into pea-sized pieces. Add the water and process until the dough comes together. Dump the dough out onto the counter and press it together with your hands, shaping it into a disk. Wrap the pastry with plastic wrap and refrigerate for 30 minutes.

Roll the pastry out into a 12-inch circle and transfer it to a 9-inch tart pan. Gently press the pastry into the bottom and sides of the pan, letting any excess fold over the sides of the tart pan. Trim away the excess pastry around the rim of the tart pan. Prick the bottom of the pastry several times with a fork so dough doesn’t bubble up while baking. Chill the tart shell in the refrigerator for at least 30 minutes.

Preheat the oven to 350°F.

Place a piece of parchment paper or a piece of greased aluminum foil on top of the pastry and fill the tart pan with pie weights or dried beans. This is called blind baking and the weights or beans will prevent the pastry from rising up and buckling as it bakes.

Bake the tart shell for 30 minutes. Then gently remove the foil and continue to bake for another 10 to 15 minutes, until the crust is golden brown. Remove the tart pan from the oven and let it cool on a cooling rack.

While the crust bakes, make the lemon curd. Combine the eggs, egg yolk, sugar, lemon juice and salt in a medium saucepan and whisk together. Place the pan over medium heat and cook the mixture, stirring constantly with a spatula, until the curd has thickened and has reached 175°F – about 8 to 10 minutes. Remove the pan from the heat and stir in the lemon zest and butter, a little at a time.

Transfer the warm lemon curd to the baked tart shell and cool to room temperature.

Make the meringue. Set up a double boiler by placing a metal mixing bowl over a saucepan of simmering water. (Make sure the bowl does not touch the water.) Add the egg whites, cream of tartar and sugar to the bowl and whisk until smooth. While slowly stirring with a spatula or spoon, cook the egg whites until they reach 160°F. The mixture should be smooth, not grainy. Remove the bowl from the heat and use an electric stand mixer or hand mixer to whip the whites at medium-high speed for about 10 minutes until stiff, glossy peaks are formed. Do not over beat.

Spread the meringue onto the cooled lemon curd, making small peaks with the back of a spoon. Let the tart cool to room temperature. (The tart can be served at room temperature or chilled. If you prefer the tart chilled, let it cool in the refrigerator, uncovered.)

Before serving, use a brulée torch to brown the peaks of the meringue. If you don’t have a brulée torch, place the tart under a hot broiler for a few minutes to toast the peaks of the meringue. Watch carefully as it can burn quickly. The tart is best served the same day it is made.