01 - Heat the oven to 350°F (175°C).
02 - Combine graham cracker crumbs, sugar, salt, and melted butter in a medium bowl. Press mixture firmly into the bottom and sides of a 9-inch pie dish. Bake for 8 to 10 minutes until lightly golden. Allow to cool completely.
03 - Whisk sugar, cornstarch, and salt in a saucepan. Gradually add water while whisking continuously. Cook over medium heat, stirring constantly, until thickened and boiling. Continue boiling for 1 minute while stirring.
04 - Lightly beat egg yolks in a separate bowl. Slowly whisk in 1/2 cup of the hot mixture to temper. Return tempered yolks to the saucepan and cook while whisking for 2 minutes. Remove from heat and stir in lemon juice, lemon zest, and butter until smooth.
05 - Pour lemon filling into the cooled crust and set aside.
06 - In a clean bowl, beat egg whites and cream of tartar until soft peaks form. Gradually add sugar, beating until stiff, glossy peaks develop. Incorporate vanilla extract with a final brief beat.
07 - Spread meringue evenly over hot lemon filling, sealing edges to the crust. Create decorative peaks using the back of a spoon.
08 - Bake at 350°F (175°C) for 15 to 18 minutes until meringue is golden brown. Cool at room temperature for 1 hour, then refrigerate at least 1 hour before serving.