Prepare the pie crust by rolling out the dough to about 1/8 inch thickness, transfer it to a pie plate, trim excess, flute the edges, and refrigerate for 30 minutes.

Preheat your oven to 425°F (220°C), line the crust with foil, fill with pie weights, and bake for 20-25 minutes until golden. Remove the foil and bake for another 5 minutes. Cool completely.

In a saucepan, whisk together sugar, cornstarch, flour, and salt. Gradually stir in water and cook over medium heat until thick and bubbling, about 8-10 minutes. Stir for another 2 minutes.

In a bowl, beat egg yolks until smooth. Temper yolks by mixing in about a cup of hot lemon mixture, whisking constantly. Return the mixture to the saucepan, bring to a boil, and stir in butter, lemon juice, and zest until combined.

In a mixing bowl, beat egg whites and 1/4 teaspoon salt on medium speed until soft peaks form. Gradually add sugar and beat until stiff, glossy peaks are achieved.

Pour lemon filling into the cooled crust, dollop meringue over the filling, create peaks and swirls, and bake at 350°F (175°C) for about 12-15 minutes until meringue is golden brown.

Let the pie cool at room temperature for about an hour, then refrigerate leftovers loosely covered for up to 2-3 days.