In a saucepan, combine the sugar, cornstarch and salt.
Add the water and constantly stirring with a whisk, bring the mixture to a boil. Reduce the heat and cook for 2 more minutes while continuing to whisk. Don't be afraid to whisk vigorously as it gets thicker.
Take 1/4 cup of the hot mixture and stir it into the fork beaten egg yolks. Return to this to the saucepan, bring to a boil, and cook for 3-4 minutes more while stirring constantly.
Stir in the butter, lemon juice, and zest and cook for another minute.
Immediately pour into the pre-baked pie crust.
For the Meringue
In a clean and cold bowl, beat the egg whites with an electric handheld beater or a stand mixer.
Add the pinch of salt, and the sugar while you mix.
Lift the beaters out when you can see soft peaks in thick foamy waves. That's when it's done.
Put the meringue on the hot lemon filling starting at the edges first. Make sure the meringue reaches all the way to the edge of the crust so there are no gaps.
Then add the rest of the meringue in the middle so that the filling is completely covered.
With the handle of a spoon or the blade of a knife, pull up some soft peaks.
Place in a preheated 375F oven for 6 minutes.
Remove from oven and let cool completely before serving.
My grandmother, Geeg, didn't have an electric beater for a long time. She either whipped her egg whites with a fork or used a hand beater. And, she didn't use cream of tartar in them either but you can add a pinch if you like!