Preheat oven to 350°F (175°C).
Mix graham cracker crumbs, sugar, and melted butter in a bowl. Press into a pie dish to form the crust.
Bake crust for 10 minutes. Let it cool.
In a saucepan, combine sugar, cornstarch, and salt. Gradually stir in water, lemon juice, and lemon zest. Cook over medium heat, stirring constantly, until mixture thickens and boils. Boil for 1 minute.
Remove from heat. Stir a small amount of hot mixture into egg yolks, then return to the saucepan. Bring to a gentle boil and cook for 2 minutes. Remove from heat and stir in butter. Pour filling into the crust.
In a mixing bowl, beat egg whites and cream of tartar until soft peaks form. Gradually add sugar, beating until stiff peaks form. Spread meringue over hot filling, sealing edges to crust.
Bake in preheated oven for 10-12 minutes, or until meringue is golden brown. Cool on a wire rack.