Combine flour, salt, and sugar in the bowl of a food processor and pulse to combine.
Cut cold butter into chunks and add to flour. Pulse until the mixture looks like pea sized crumbs.
With the food processor running, slowly drizzle in the water until the dough just begins to clump together but there are still loose crumbs. You may not need all the water.
Dump into a clean surface and form dough with hands until all moistened and it forms one ball of dough. Form into a disc and wrap with plastic, chill 30 minutes minimum.
Preheat your oven to 350°F and roll out your pie dough on a floured surface. Fit it into your pie plate and trim any excess. Freeze for 5 to 10 minutes.
Line with foil and fill with pie weights or dried beans. Bake for 30 minutes.
Remove pie weights and foil and return to the oven to bake another 10 to 15 minutes, or until golden brown and baked through. Let cool on the counter.
Lemon Filling
Combine the cool water and cornstarch in a small saucepan and stir until cornstarch has dissolved and no lumps remain.
Add in lemon juice, zest, salt, and sugar and stir to combine. Bring to a boil over medium heat, continuously stirring until it forms a clear, thick gel. Remove from heat.
Using a fork or whisk, gently dip it into the hot lemon filling and quickly whisk what clings to the fork or whisk into the egg yolks. Repeat, adding small amounts at a time, until you’ve whisked about half the mixture into the egg yolks.
Add the egg yolk mixture back into the pot with the remaining filling and stir to combine.
Add in the butter and stir until melted. Return the pot to the stove and bring to a gentle boil for 2 minutes while stirring. Set aside to cool slightly while you make your meringue.
Italian Meringue
In a small saucepan over medium heat combine the sugar and water. Stir to combine and bring to the soft ball candy stage, or 240°F.
While your sugar syrup cooks, add your egg whites, cream of tartar, salt, and vanilla into the very clean bowl of your stand mixer.
Beat on medium low to medium speed until it gets to the soft peak stage. When you pull the beater from the egg white, the tip of any meringue on it will droop slightly over, but not fall off the beater.
Turn your mixer up to medium high and begin slowly drizzling in the sugar syrup while it runs. Be sure the stream of syrup is no thicker than a toothpick as you add it.
Once all the sugar syrup is added, continue to beat until it’s glossy and holds a stiff peak: the tip of the meringue when lifted on the beater will stand tall and straight.
Assembly
Pour the warm filling into the cooled pie crust. Smooth it down so it’s level, then using a spatula or parchment paper, rough up the surface so it looks like spackle or a textured wall.
Working from the edges into the middle, spoon on your meringue, smoothing it down completely against the crust on all sides to prevent slipping.
Build the meringue into a smooth, even dome.
Toast under the broiler on high by carefully rotating the pie about 6 inches under the broiler until browned. You can also use a blow torch.
Let it cool for 3 hours before slicing and serving.
Notes
*Use a prebaked, store bought, or no bake graham cracker crust if you prefer. *3 lemons was just right for juice and zest.