In a large mixing bowl, combine all-purpose flour, powdered sugar, and salt. Mix until thoroughly combined.
Add the unsalted butter that’s been cut into cubes. Using your fingertips, rub the butter into the flour mixture until it resembles coarse breadcrumbs, with a few larger pieces remaining.
Next, add a large egg and cold water to the bowl. Mix with a fork until all ingredients are well incorporated.
Bring the dough together with your hands and lightly knead it in the bowl for a few seconds. Form it into a ball and cover it in plastic wrap. Let it chill in the refrigerator for one hour.
Once the dough has chilled, remove it from the fridge and let it sit for 15 minutes at room temperature. Meanwhile, preheat your oven to 350°F.
On a lightly floured surface, roll out the dough to about 3mm in thickness, forming a circle approximately 12 inches in diameter.
Carefully transfer the dough into a 9-inch tart pan. Gently press the dough into the bottom and edges of the pan. Trim any excess dough from the edges.
Line the tart shell with baking parchment and fill it with pie weights or uncooked rice. Blind bake for 15 minutes, then remove the weights and parchment.
In a small bowl, mix together the lemon zest, lemon juice, and cornstarch until no lumps remain.
In a medium saucepan, bring water to a boil. Add the lemon mixture and reduce the heat to medium-low, stirring continuously.
In a separate mixing bowl, combine granulated sugar and egg yolks. Mix until smooth, then gradually stir into the thickened lemon mixture.
While the filling cools, prepare the meringue. In a clean bowl, add egg whites and beat on low until frothy. Increase the speed to medium until soft peaks form.
Once all sugar is added, increase the speed to high and beat for five minutes until glossy. Test by rubbing a bit between your fingers.
Now it’s time to assemble! Pour the cooled lemon filling into the baked crust. Then, swirl the meringue on top with a piping bag.
To finish, use a chef’s blow torch to scorch the meringue, or place it under a hot broiler for a couple of minutes, watching carefully.
Slice, serve, and enjoy your homemade Lemon Meringue Tart!
