Combine the vanilla pudding and lemon gelatin in a medium saucepan. Whisk in the water and lemon juice until combined.
Place over medium heat and cook until the lemon mixture comes to a boil, stirring occasionally. Continue to cook for 3 more minutes. Remove from the heat and allow to cool for 10 minutes.
Pour the lemon filling into the graham cracker pie shell and spread it out evenly. Cover the pie with plastic wrap so that it touches the surface to prevent a skin from forming.
Refrigerate the pie until set, about 4 hours.
Once the pie is set, make the meringue. Pour the egg whites into a large mixing bowl. Using a stand mixer or hand mixer, beat until the egg whites are frothy. Add the sugar and cream of tartar. Continue to beat until stiff peaks form.
Dollop the meringue over the filling. Spread it out toward the edges using an offset spatula. Use the spatula or the back of a spoon to create swirls/whorls in the meringue.
Using a butane torch, carefully brown the meringue to your desired doneness.
Cut into 8 slices and enjoy or refrigerate until ready to serve.
Notes
I used 2 packages of "family size" cook-and-serve pudding mix. If you can only find the smaller 3-ounce boxes, you'll want to use 3 packages.