• Preheat the oven to 350 degrees F.

Prepare the pie crust.

• Combine the all-purpose flour, unsalted butter, granulated sugar, and salt. Combine these ingredients in a food processor until they resemble coarse crumbs, then add 4 to 5 tablespoons of ice water, mixing until the dough holds together.
• Roll it out and fit it into a 9-inch pie pan, then bake at 350°F for about 15 minutes. Set aside.

Prepare lemon filling.

• Whisk together granulated sugar, cornstarch, and a pinch of salt in a saucepan. Stir in 1½ cups of water and cook over medium heat until thickened. Reduce heat and add 3 large egg yolks (beaten), 1/2 cup of freshly squeezed lemon juice, and 2 tablespoons of lemon zest. Cook for an additional 2 minutes before removing from heat and stirring in 2 tablespoons of unsalted butter.
• Pour the filling into the baked pie crust.

Prepare the meringue.

• Beat 3 egg whites until soft peaks form, then gradually add 1/4 cup of granulated sugar while continuing to beat until stiff peaks form. Spread the meringue over the lemon filling, sealing the edges to prevent shrinking.
• Finally, bake the pie at 350°F for 10-15 minutes or until the meringue is golden brown. Allow the pie to cool before serving.