Bake your pie crust according to recipe or package directions until golden and fully baked. Let it cool slightly while you prepare the filling.

A fully baked crust is important so it doesn’t turn soggy under the lemon filling.

In a medium saucepan, whisk together sugar, cornstarch, and salt. Slowly whisk in the water until smooth.

Place the saucepan over medium heat and cook, whisking constantly, until the mixture thickens and starts to bubble. This usually takes about 5–7 minutes.

Once thick, reduce the heat. Slowly whisk a small amount of the hot mixture into the beaten egg yolks to temper them. Then pour the egg mixture back into the saucepan.

Cook for 2 more minutes, stirring constantly, until thick and glossy.

Remove from heat and stir in lemon juice, lemon zest, and butter until smooth.

Pour the hot lemon filling directly into the baked pie crust.

In a clean mixing bowl, beat the egg whites and cream of tartar on medium speed until soft peaks form.

Gradually add the sugar, one tablespoon at a time, beating until stiff, glossy peaks form. Beat in vanilla extract.

The meringue should be smooth, shiny, and hold its shape.

Spoon the meringue over the hot lemon filling, starting at the edges and sealing it to the crust. This helps prevent weeping.

Use the back of a spoon to create soft peaks and swirls.

Bake in a preheated oven at 350°F (175°C) for 12–15 minutes, or until the meringue is lightly golden on top.

Remove from oven and let cool at room temperature for at least 2 hours before slicing.