Make the Crust:
Spray a 9×13-inch baking dish with nonstick spray and line it with parchment paper, leaving an overhang on both long sides.
In a food processor, pulse the flour, cornstarch, salt, and powdered sugar to combine. Add cold butter and pulse until the mixture resembles crumbs (10-15 seconds).
Press the mixture evenly into the prepared pan, slightly up the sides. Refrigerate for 30 minutes (or freeze for 15 minutes).
Preheat the oven to 350°F and bake for 15-20 minutes, until the edges are golden.

Make the Lemon Filling:
While the crust bakes, whisk together eggs, granulated sugar, flour, lemon juice, and lemon zest in a large bowl until the mixture is smooth and no lumps remain.
After the crust is baked, quickly stir the lemon filling and pour it over the crust.
Bake the assembled bars for 20-25 minutes, until the top is lightly browned and the custard is set.
Let cool to room temperature before refrigerating until fully chilled and firm.

Assemble and Cut the Bars:
Once chilled, lift the bars using the parchment overhang and transfer them to a cutting board.
Cut into even squares, cleaning the knife between slices for clean edges. Dust with powdered sugar.

Make the Meringue:
Beat egg whites with an electric mixer until frothy, gradually adding granulated sugar until stiff peaks form.
Pipe or spoon the meringue onto the cooled lemon bars.
Lightly brown the meringue with a kitchen torch or broil under high heat for 1-2 minutes, keeping an eye on them.

Serve and Enjoy!