For the Pie:
9-inch pie crust, baked (either buy a frozen pie crust already in an aluminum tin, or buy frozen pie crust that needs to be defroster/rolled out/placed in a pie plate)
For the Pie Filling:
cup granulated sugar
tbsp all-purpose flour
tsp Kosher salt
For the Meringue:
tbsp white sugar
tsp cream of tartar
lemons, juiced and zested
Preheat oven to 350
Bake the pie crust according to package instructions.
For the lemon filling, whisk together 1 cup of sugar, flour, cornstarch, and salt in a medium saucepan. Over medium-high heat, whisk in water, lemon juice, and lemon zest. Stir frequently until mixture comes to a boil. Stir in butter. Place beaten egg yolks in a medium bowl and gradually whisk in ½ cup of the hot sugar mixture. Whisk the egg yolk mixture back into the rest of the sugar mixture. Bring to a boil and continue to cook and stir constantly until it thickens. Remove from heat and pour the filling into a baked pastry shell.
For the meringue, in a large glass or metal bowl, whip egg whites until foamy with a hand mixer. Add cream of tartar and sugar gradually and continue to whip until stiff peaks form. Spread meringue over pie.
Bake in preheated oven for 15-20 minutes, or until meringue is golden.
Sit for an hour at room temperature, then 3 hours in the refrigerator before consuming.