Instructions

For the Crust:

1. Prepare ½ cup ice-cold water and keep in fridge. In a food processor, pulse flour, sugar and salt. Add in half of the butter and pulse for 30 seconds. Add in the rest of butter and pulse until the mixture looks like coarse meal.
2. Sprinkle about 6 tablespoons cold water over mixture and pulse until dough comes together in clumps. If dry, add a little bit more water (1 teaspoon at a time) until dough comes together. Remove dough from processor and pat into a disk.
3. Divide dough into two disks; one slightly bigger than the other and wrap in plastic wrap. Chill for at least an hour or overnight. The dough can be made up to 3 days ahead. Keep chilled.
4. Let stand at room temperature a few minutes before rolling out.
5. Roll out larger disk on a lightly floured surface to a large circle. Fit into an ungreased 9-inch pie dish, trim the edges leaving an inch or two overhang. Refrigerate for 30 minutes.
6. Preheat oven to 425 degrees. Line the crust with buttered parchment or foil and fill with pie weights.
7. Bake the crust for 20 minutes. Then remove the pie weights and lining. Continue baking for 10-15 minutes until crust is lightly brown. Let cool completely.

For the Lemon Filling:

1. Place the butter in a medium bowl. Set the bowl in a larger bowl filled with ice water. Place a fine mesh sieve over the bowl with butter. Set aside.
2. In another small bowl, whisk the egg yolks.
3. In a medium saucepan, whisk together sugar, cornstarch and salt with 1 1/2 cup water. Set over medium-high heat and whisking constantly until mixture thickens and bubbling, about a minute.
4. Remove mixture from heat and gradually whisk in half of the mixture into the egg yolks. Pour the egg yolk mixture back into the saucepan and whisk in along with the lemon zest and juice.
5. Reduce heat to medium-low, cook mixture, stirring constantly, until mixture is bubbling and thickens, about two minutes.
6. Immediately pour the custard over the prepared fine sieve. Press through the sieve into the bowl with butter. Stir until butter is melted and mixture is cool, about 5 minutes.
7. Pour into the chilled crust and cover with a plastic wrap pressing directly onto the surface. Chill until set, about 8 hours.

For the Topping:

1. In the bowl of the stand mixer fitted with the whisk attachment, beat the egg whites, vanilla extract, cream of tartar and salt on medium-high speed until soft peaks form, about 2 minutes. With mixer running, gradually add in the 3 tablespoons sugar.
2. Meanwhile, in a small saucepan bring to boil the 1/2 cup sugar, lemon juice and 2 tablespoons water, stirring until sugar melts. Cook, without stirring, until a thermometer reads 240 degrees, about 4 minutes.
3. Immediately remove from heat and gradually stream into the egg whites with mixer running. Increase speed to high and beat until the meringue is glossy and stiff and the bowl feels cool to the touch.
4. Top the pie with the meringue and use a kitchen torch to toast the top of the meringue.