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