Prepare the Pie Crust:

1. Add the flour, sugar, lemon zest, and salt to the bowl of a food processor. Pulse until well combined. Add in the butter and cream cheese and pulse 5 to 7 times, or until the butter is broken down into tiny pebbles.
2. With the processor running, add in the water and let the dough process until it forms a cohesive ball around the blade, about 1 minute.
3. Remove the dough from the processor. You can roll it out now or roll it out later, just chill it in the refrigerator for at least 30 minutes and up to 2 days.
4. On a well-floured work surface, roll out the pie dough to an 11-inch circle. Fit the pastry into a 9-inch pie plate, making sure to press the pastry into the sides and the bottom. Crimp the edges as desired.. Prick the bottom of the dough all over with a fork. Place the pie shell in the freezer while the oven preheats, at least 15 minutes.
5. Preheat the oven to 375ºF.
6. Once chilled, line the pie shell with a round piece of parchment paper, then add pie weights (I recommend dry rice, beans, or lentils), pushing the pie weights to the edges.
7. Bake the crust for 20 minutes, then remove it from the oven and carefully remove the parchment and pie weights. Return the empty pie shell back to the oven to continue to bake for an additional 10 to 12 minutes, or until the pastry is fully cooked through. Set aside until ready to use.

Make the Lemon Filling: 

1. In a medium enameled or stainless steel pot, whisk together the sugar, cornstarch, and salt. Whisk in the egg yolks, water, and lemon juice until fully combined. Turn on the heat to medium and cook, whisking constantly and occasionally using a rubber spatula to scrape up any thickened lemon filling from the edges of the pot, until the filling has completely thickened and large bubbles are forming and popping, about 8 minutes. 
2. Remove from the heat and immediately pour through a fine-mesh nylon or stainless steel strainer into a bowl, using the spatula to push all the filling through the strainer while leaving behind any bits of cooked egg. Whisk in the butter and lemon zest until fully combined.
3. Pour the filling into the prepared pie crust and smooth over the top. Let cool to room temperature before chilling in the refrigerator for at least 3 hours or overnight.

Make the Meringue:

1. Fill a small, sturdy pot with at least 1 ½ inches of water and turn on the heat to medium-high. This is the bottom of your makeshift double boiler.
2. In a heatproof bowl (the metal bowl from your electric mixer is perfect here), combine the egg whites, sugar, salt, and cream of tartar. Whisk together until fully combined.
3. Set the bowl over the pot of steaming water. Alternate between whisking the mixture and scraping down the sides of the bowl with a rubber spatula until the egg whites reach a temperature at 160°F and all the sugar has dissolved, roughly between 8 and 10 minutes (see note for troubleshooting). .
4. Remove the mixture from the heat and attach the bowl to an electric stand mixer fitted with the whisk attachment. Turn the mixer on at the lowest speed, then gradually increase the speed until it reaches medium-high. With the mixer running, add in the vanilla.
5. Whip until the meringue is glossy and begins to pull away from the sides of the bowl, about 8 minutes. It should have stiff peaks and should be cooled down significantly.
6. Transfer half of the meringue to the top of the pie. Using an offset spatula, spread it evenly over the lemon filling. Dollop the remaining meringue on top and swoosh around with a spoon.
7. To caramelize the top of the meringue, use a kitchen torch or place the pie under the broiler for 2 to 4 minutes, watching closely so it does not burn.
8. Serve within 4 hours, keeping chilled until ready to serve.