Gather all of the ingredients listed and preheat your oven to 325 degrees F (165 degrees C) to ensure the pie is ready to go in once assembled.

In a medium saucepan, whisk together the granulated sugar, all-purpose flour, cornstarch, and salt. Stir in the water, lemon juice, and lemon zest. Cook over medium-high heat, stirring frequently, until the mixture comes to a boil and thickens slightly. Once boiling, stir in the butter until melted and well combined.

Place the beaten egg yolks in a small bowl. Gradually whisk in about 1/2 cup of the hot sugar mixture to temper the yolks. Then, whisk the egg yolk mixture back into the saucepan with the remaining sugar mixture. Bring the mixture to a boil once more and cook, stirring constantly, until it thickens to a custard-like consistency. Remove from heat.

Pour the hot lemon filling (from Step 3) into the pre-baked pie shell, spreading it evenly. This step sets the stage for your luscious lemon meringue layers. I like to let the filling sit for just a minute to slightly cool before topping with the meringue.

Beat the egg whites in a clean glass, metal, or ceramic bowl with an electric mixer until foamy. Gradually add the granulated sugar, continuing to beat until stiff peaks form. Make sure there is no trace of yolk to achieve maximum volume—I find using a metal bowl helps the egg whites whip up better.

Working quickly, spread the meringue (from Step 5) over the warm lemon filling (from Step 4), making sure to seal the edges to the crust. Use the back of a spoon to create decorative peaks on top if desired. Bake the pie in the preheated oven for 20 to 25 minutes, or until the meringue is golden brown.

Remove the baked pie from the oven and let it cool completely before slicing and serving. This helps the filling set and makes for cleaner slices. For an extra refreshing touch, I sometimes chill the pie for an hour before serving.