Preheat the oven to 350°F (175°C). Fit the pie crust into the pie dish and prick the bottom with a fork. Bake for 10-12 minutes until lightly golden. Remove from oven and let cool.

In a saucepan, whisk together sugar, cornstarch, and salt. Gradually stir in water. Cook over medium heat, stirring constantly until the mixture thickens and bubbles.

Remove from heat. Stir a small amount of the hot mixture into the egg yolks, then return to the saucepan. Add lemon juice, lemon zest, and butter. Stir until smooth.

Pour the lemon filling into the baked pie crust.

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

Spread the meringue over the lemon filling, making sure to seal the edges.

Bake in the preheated oven for 10-15 minutes, or until the meringue is golden brown. Remove from oven and let cool before serving.