Preheat your oven to 350°F (175°C) and prepare your pie crust by placing a pre-made crust in the pie dish or pressing graham cracker crumbs mixed with sugar and melted butter into the pie dish.

Bake the crust in the preheated oven for 8-10 minutes until lightly golden. Remove and allow to cool.

In a medium saucepan, whisk together 1 cup of sugar, cornstarch, and salt. Gradually add in the water while continuing to whisk. Cook over medium heat, stirring constantly, until the mixture comes to a boil and thickens.

Once thickened, reduce the heat and whisk a small amount of the hot mixture into the egg yolks to temper them, then whisk the tempered egg yolks back into the saucepan. Cook for an additional 2 minutes, stirring constantly.

Remove from heat and stir in the lemon juice, lemon zest, and butter until smooth. Pour the lemon filling into the cooled pie crust.

In a clean mixing bowl, beat the egg whites and cream of tartar until soft peaks form. Gradually add the sugar and continue to beat until stiff peaks form.

Spread the meringue over the lemon filling, sealing the edges to prevent shrinking, and create peaks or swirls for decoration.

Bake in the oven for 10-15 minutes until the meringue is lightly browned, watching closely to avoid burning.

Remove from the oven, let the pie cool to room temperature, then refrigerate for at least 2 hours before serving for the best texture.