Creating this divine Key Lime Meringue Pie is straightforward when you follow these detailed steps:

1. Preheat Oven: Set your oven to 350°F (175°C) to preheat.
2. Prepare Crust: In a bowl, combine graham cracker crumbs, sugar, and melted butter. Mix until crumbly.
3. Form the Crust: Press the crumb mixture into the bottom and up the sides of a 9-inch pie pan to form an even layer.
4. Bake the Crust: Place the crust in the preheated oven and bake for 8-10 minutes until golden. Remove and let cool.
5. Make Filling: In a mixing bowl, whisk together egg yolks and sweetened condensed milk until well blended.
6. Add Key Lime Juice: Stir in key lime juice and lime zest until combined.
7. Pour Filling: Pour the lime mixture into the cooled crust and spread it evenly.
8. Bake Filling: Bake the pie for another 15 minutes in the oven. This helps set the filling.
9. Prepare Meringue: While the pie bakes, beat egg whites in a separate bowl. Add cream of tartar and continue beating until soft peaks form.
10. Add Sugar: Gradually add sugar while beating until stiff peaks form. Mix in vanilla extract.
11. Top with Meringue: Once the pie has finished baking, remove it from the oven and immediately spread the meringue on top of the filling. Make sure to spread it all the way to the edges to prevent shrinking.
12. Bake Again: Return the pie to the oven for an additional 10-15 minutes until the meringue is golden brown.
13. Cool & Chill: Remove the pie from the oven and let it cool for at least an hour. Refrigerate for at least 2 hours before serving to ensure it’s nicely chilled.