01 - Set oven temperature to 350°F.
02 - Combine graham cracker crumbs, sugar, melted butter, and salt in a bowl. Mix until texture resembles wet sand. Press firmly into bottom and sides of a 9-inch pie dish.
03 - Bake crust for 8 to 10 minutes until lightly golden. Remove from oven and allow to cool slightly.
04 - In a saucepan, whisk together sugar, cornstarch, and salt. Gradually add water while whisking. Cook over medium heat, stirring constantly, until mixture thickens and bubbles, approximately 3 to 5 minutes.
05 - Whisk egg yolks separately. Slowly whisk a small amount of the hot mixture into yolks to temper. Return yolk mixture to saucepan and continue cooking for 2 minutes, stirring constantly until thickened.
06 - Remove from heat. Stir in lemon juice, lemon zest, and butter until fully incorporated and smooth.
07 - Pour lemon filling into the prepared crust.
08 - In a clean bowl, beat egg whites and cream of tartar until soft peaks form. Gradually add sugar, beating until stiff, glossy peaks form. Mix in vanilla extract.
09 - Spread meringue over warm filling, ensuring it touches crust edges to seal. Create decorative peaks with a spatula.
10 - Bake for 15 to 18 minutes until meringue is golden brown.
11 - Cool pie at room temperature for 1 hour, then refrigerate for at least 1 hour before serving.