01 - Preheat oven to 350°F.
02 - Combine graham cracker crumbs, sugar, melted butter, and salt in a medium bowl until mixture resembles wet sand. Press evenly into bottom and up sides of a 9-inch pie dish. Bake for 10 minutes. Cool on wire rack.
03 - Whisk together sugar, cornstarch, and salt in a medium saucepan. Gradually whisk in water until smooth. Cook over medium heat, stirring constantly, until mixture thickens and comes to a gentle boil, about 5 minutes.
04 - Lightly beat egg yolks in a small bowl. Slowly whisk in ½ cup of the hot mixture to temper. Return egg yolk mixture to saucepan. Cook, stirring constantly, for 2 minutes.
05 - Remove from heat. Stir in lemon juice, lemon zest, and butter until smooth. Pour filling into cooled crust.
06 - Beat egg whites and cream of tartar in a clean bowl with electric mixer until soft peaks form. Gradually add sugar, beating until stiff, glossy peaks form. Beat in vanilla.
07 - Spread meringue over hot lemon filling, ensuring it touches crust to seal. Create decorative swirls on top.
08 - Bake pie for 12 to 15 minutes until meringue is golden brown. Cool completely, then refrigerate for at least 2 hours before serving.