Line up all the ingredients and have everything ready to go.

Prepare the meringue as directed at the bottom or wait and prepare it after you make the filling. I prefer to make the meringue first so that it's ready to go and I can quickly slather it on top of a piping hot filling.

Mix the sugar, cornstarch and salt in a large (3 ½ quart) non-aluminum saucepan.

Whisk the egg yolks, milk and lemon juice together in a bowl. Whisk the milk mixture into the saucepan with the sugar mixture and turn heat to medium. Whisk constantly until mixture begins to boil -- this could take anywhere from five to 10 minutes. When mixture begins to thicken and boil, boil for 1 minute, whisking constantly. Remove from heat and whisk in the lemon zest, butter and vanilla. Pour into the pie shell and immediately spoon meringue around the edges to seal. Spoon remaining meringue over the center and cover all of the lemon filling.

Bake at 325 F for about 25 minutes. Let cool at room temperature, then transfer to the refrigerator and chill for several hours.

Meringue: Beat the egg whites until foamy, then add the cream of tartar. Continue beating until soft peaks form, then beat in the sugar a few tablespoons at a time along with the cornstarch.