Method

Preheat oven to 375 degrees
Bake the pie shell for 25 mins. in the oven. While the pie shell is baking you can start your lemon filling.
In a saucepan over medium heat add the cornstarch, water, sugar, salt and lemon juice and mix well.
Stir in the egg yolks one at a time until incorporated. Bring to a gentle bubble (about 8 mins) then stir in the butter. Mix constantly.
Once the mixture is thick you pour it into your baked pie shell and set aside.
To make the meringue add the 4 egg whites to a mixing bowl of a standing mixer and use the whisk attachment.
Start to beat the whites on high speed. Reduce speed to add the cream of tartar and sugar; then increase the speed and beat until stiff peaks form. Approximately 3-4 minutes.
Add the stiff egg whites on top of the lemon filling, and spread evenly and completely cover the filling. Bake for 10-12 mins. in the oven or until golden brown.