Using a food processor, pulse together the flour, sugar and salt until combined. Add butter and pulse until mixture becomes coarse meal, about 15 pulses.
In a small bowl, combine egg yolk, water and vanilla extract. Add the egg mixture to food processor and pulse until it starts to clump together. DO NOT pulse until ball is formed. It should be crumbly with large clumps of dough.
Turn dough only a lightly floured surface and form into a disk. Wrap in plastic wrap and put in fridge for at least 1 hour or up to 3 days.
Remove dough from the fridge about 10 minutes before you begin rolling. On a lightly floured surface, roll the dough so that it is about 3 inches longer than you pie dish and is between ⅛ inch and ¼ inch in thickness. Press the dough into the bottom and along the sides of the pie plate, being careful not to puncture the dough. Crimp edges of pie. Place pie crust back in fridge for 30 minutes.
While the crust is chilling, preheat oven to 400°F and place baking sheet in the oven. Crunch up some parchment paper and line pie crust with it. Fill with pie weights, dried beans or rice, making sure they are evenly distributed.
Place pie on preheated baking sheet and bake until the edges of the crust are beginning to brown, about 15 minutes. Remove the pie from the oven and take out the parchment paper with the weights. Poke holes around the bottom of the crust with a fork and place back in the oven, baking for another 7-8 minutes, or just until the bottom is begging to brown. Remove from oven and reduce temperature to 350°F.
While pie crust in baking heat a large saucepan over medium heat and add the water, sugar, lemon juice, cornstarch, lemon zest and salt and cook until slightly thickened and bubbly, about 6-7 minutes. Reduce heat to low once thickened.
Take the egg yolks and whisk in a medium bowl. Slowly pour a few spoonfuls of the hot lemon mixture into the eggs, whisking constantly. Then very slowly pour the egg mixture into the lemon mixture and turn the heat back up to medium. Cook until thickened and starting to bubble, about 2-3 minutes. Remove from heat and stir in the butter and vanilla extract.
Evenly spread the lemon filling over the warm partially baked pie crust. Cover with plastic wrap while you make the meringue.
Place the egg whites, cream of tartar, and vanilla extract in the bowl of a stand mixer fitted with the whisk attachment and beat on high for 3-4 minutes, or until soft peaks form. Slowly add the sugar and beat on high for another 2 minutes, or until stiff peaks form.
Spread the meringue on the top of the lemon mixture in peaks, making sure that the meringue touches the crust and none of the lemon filling shows through.
Bake at 350°F for 25-30 minutes or until the meringue is browned, Cool at room temperature for one hour, then chill in the fridge for at least 4 hours before slicing.