Prepare the Pie Crust:

1. Add the flour, sugar, lemon zest and salt to the bowl of a food processor, and pulse until well combined. Add in the cream cheese and butter and pulse 5-7 times, or until the butter is broken down into tiny pebbles.
2. With the motor running, add in the water and let the dough process until it forms together into 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 up to 2 days.
4. On a well-floured work surface, roll out the pie dough to an 11″ circle, line a 9” pie plate, and crimp the edges as desired. Prick the bottom of the dough all over with a fork. Place the pie in the freezer while the oven preheats, at least 15 minutes.
5. Preheat the oven to 375ºF.
6. Once chilled, line the pie dough with a round piece of parchment paper and then add pie weights (or dry rice or beans or lentils), making sure to push pie weights to the edges.
7. Blind bake the crust for 20 minutes, then remove 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 10-12 minutes, or until the pastry is fully cooked through. Set aside until ready to use.

Make the Lemon Filling: 

1. Whisk together cornstarch, sugar, and salt. Whisk in the egg yolks, water and lemon juice until fully combined. Turn on the heat to medium and cook the mixture, whisking constantly, and occasionally taking a spatula and scraping up any thickened lemon filling in the edges of the pan. Cook until the filling has completely thickened and large bubbles are forming and popping, about 8 minutes. 
2. Remove from heat; immediately pour through a fine-mesh strainer into a bowl, using a spatula to push all the filling out while leaving behind any bits of cooked egg. Whisk in the zest and butter until fully combined.
3. Pour the pudding into the prepared pie crust and smooth over the top. Let cool at 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 make-shift double boiler.
2. Combine the egg whites, salt, sugar, and cream of tartar to a heat-proof bowl (the metal bowl from your electric mixer is perfect here) and 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 spatula, until egg whites reach a temperature at 160°F, roughly between 8 and 10 minutes, and all the sugar has dissolved (see note for troubleshooting).
4. Remove the mixture from the heat and attach the bowl to an electric stand mixer fitted with a whisk attachment. Turn the mixer on the lowest speed, and gradually increase the speed until it reaches medium-high speed. 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 be cooled down significantly.
6. Transfer half of the meringue on top of the pie. Using an offset spatula spread it evenly on top of the lemon filling. Transfer the remaining meringue on top, and swoosh around with a spoon.
7. To torch the top of the meringue, use a kitchen torch or place the pie under the broiler for 2-4 minutes, watching closely so it does not burn.
8. Serve within 4 hours, keeping chilled until ready to serve.