01 - Preheat oven to 350°F. Position oven rack in center position.
02 - Combine graham cracker crumbs, sugar, melted butter, and pinch of salt in medium bowl. Stir until mixture resembles wet sand. Press evenly into bottom and up sides of 9-inch pie dish.
03 - Bake crust for 10 minutes until lightly golden and fragrant. Transfer to wire rack to cool completely while preparing filling.
04 - Whisk together sugar, cornstarch, and salt in medium saucepan. Gradually whisk in water until smooth and no lumps remain.
05 - Cook mixture over medium heat, stirring constantly with whisk or heat-proof spatula, until thickened and comes to gentle boil, about 5 minutes. Mixture will bubble and appear translucent.
06 - Lightly beat egg yolks in small bowl. Slowly whisk about ½ cup hot mixture into yolks, whisking constantly to prevent curdling. Return tempered yolk mixture to saucepan.
07 - Cook over medium-low heat, stirring constantly, for 2 minutes to fully cook yolks and activate starch. Remove from heat. Stir in lemon juice, zest, and butter until smooth and butter melts.
08 - Pour hot lemon filling into cooled graham cracker crust. Smooth top with spatula. Set aside while preparing meringue.
09 - Beat egg whites and cream of tartar in clean, grease-free bowl with electric mixer on medium speed until soft peaks form when beaters are lifted.
10 - Increase speed to high. Gradually add sugar, 1 tbsp at a time, beating until stiff, glossy peaks form and sugar dissolves completely, about 3-4 minutes. Beat in vanilla extract.
11 - Spread meringue over hot lemon filling, ensuring meringue touches crust completely to prevent shrinking. Create decorative swirls with back of spoon.
12 - Bake pie for 12-15 minutes until meringue peaks are golden brown. Watch carefully to prevent burning.
13 - Cool pie completely on wire rack, about 1 hour. Refrigerate for at least 2 hours until filling is completely set. Store refrigerated.