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