Perfect Lemon Meringue Pie

For the filling:
1. Preheat your oven to 350 F.
2. Get all of your ingredients ready to go: squeeze your lemons and grate the zest so that your filling can come together nicely. Have the water measured out and set aside.
3. Whisk sugar, cornstarch, and salt in a medium saucepan. Then whisk in the water, fresh lemon juice, and lemon zest until blended well.
4. Whisk in egg yolks until no yellow streaks remain. Add unsalted butter.
5. Stirring constantly with a wooden spoon or rubber spatula, bring the mixture to a simmer over medium heat, then cook for one minute. The filling should be very thick.
6. Pour the filling into a pre-baked pie crust in a 9-inch pan.
7. Immediately prepare the meringue topping (recipe and preparation follows), and place it over the warm filling.

For the meringue:
1. In a clean, grease-free glass or metal bowl, beat egg whites on medium speed until foamy.
2. Add cream of tartar and beat until soft but definite peaks form.
3. Very gradually beat in sugar. Beat on high speed until the peaks are stiff and glossy, but not dry.
4. Add vanilla and vinegar and mix to combine.
5. Immediately spread the meringue over the hot pie filling, anchoring it to the edge of the crust at all points. Place meringue very close to the crust, and spread it inward.
6. Bake in your preheated oven for 20 minutes (or until meringue has a nice brown top). The pie can be stored for up to three days in the refrigerator.
7. Serve at room temperature or cold.