To prepare the crust, spray the bottom and sides of a 9-inch pie pan lightly with nonstick baking spray. Using a paper towel, wipe away any excess grease.
Combine graham cracker crumbs, granulated sugar, and melted butter in a large bowl. Just mix until it resembles wet sand.
Fill your pie pan with the crust and press firmly into the bottom and sides - the tighter you pack the crust, the less crumbly it will be! Let the crust freeze for one hour.
during the graham cracker crust setting in the freezer, prepare the lemon pudding. In a large microwave-safe bowl, stir together pudding mix and whole milk. For 8 minutes, microwave the pudding, stirring every 2 minutes.
Typically, the pudding is thick and bubbling after 8 minutes - if it does not coat the back of a spoon, continue to cook it for two additional minutes.
Whisk in the lemon juice and lemon zest, as well as the vanilla extract. Put a piece of cling wrap directly on the pudding's surface and place it in the fridge until you see the crust set.
After the crust and pudding are chilled, carefully pour the pudding into the crust and spread it out evenly. Put the pie back in the fridge for 3 hours to set.
Making the meringue is the last step before you serve the pie. Bring a small saucepan of water to a simmer over medium heat. Over the pot, place a heatproof bowl, ensuring that it does not touch the surface.
Pour the egg whites, sugar, and cream of tartar into the bowl. Stir constantly for 4 to 5 minutes, or until 165 degrees F is reached on an instant-read thermometer.
Place the egg white mixture in the bowl of a stand mixer fitted with the whisk attachment. For 3 to 4 minutes, beat on medium speed until stiff peaks form. Mix in the vanilla just until combined.
If desired, toast the meringue on top of the pie with a kitchen torch. Both plain and toasted, this meringue is delicious!