Preheat the oven to 350°F (175°C).
Make the crust: In a bowl, mix together the graham cracker crumbs, sugar, and melted butter until well combined. Press the mixture into the bottom and up the sides of a 9-inch pie dish. Bake for 10 minutes, then remove from the oven and set aside to cool.
Make the filling: In a medium saucepan, whisk together the sugar, cornstarch, and salt. Gradually whisk in the water until the mixture is smooth. Place the pan over medium heat and cook, stirring constantly, until the mixture thickens and comes to a boil.
In a separate bowl, whisk together the egg yolks and lemon juice. Gradually whisk in about 1/2 cup of the hot sugar mixture to temper the egg yolks, then whisk the egg yolk mixture back into the remaining sugar mixture in the saucepan.
Cook the mixture, stirring constantly, for an additional 2-3 minutes, until it thickens even more. Remove from heat and whisk in the butter and lemon zest until smooth.
Pour the lemon filling into the cooled crust.
Make the meringue: In a large bowl, beat the egg whites and cream of tartar with an electric mixer until soft peaks form. Gradually add the sugar, beating until stiff peaks form and the mixture is glossy.
Spread the meringue over the lemon filling, being sure to spread it all the way to the edges of the crust to seal in the filling.
Bake the pie for 10-12 minutes, until the meringue is lightly browned. Allow the pie to cool completely before slicing and serving. Enjoy
