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 firmly into bottom and up sides of a 9-inch pie dish.
03 - Bake crust for 8 to 10 minutes until lightly golden. Remove from oven and cool slightly.
04 - In a saucepan, whisk together sugar, cornstarch, and salt. Gradually add water while whisking. Cook over medium heat, whisking constantly, until thickened and bubbling, about 3 to 5 minutes.
05 - Slowly whisk a small amount of the hot lemon mixture into the beaten egg yolks to temper. Return yolk mixture to the saucepan.
06 - Continue cooking and stirring for 2 more minutes until thickened. Remove from heat and stir in lemon juice, 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 form. Beat in vanilla extract.
09 - Spread meringue evenly over the warm lemon filling, sealing the edges to the crust. Create decorative peaks with a spatula.
10 - Bake for 15 to 18 minutes until meringue is golden brown.
11 - Allow pie to cool at room temperature for 1 hour, then refrigerate for at least 1 hour before serving.