Tangy lemon meringue pie with a billowy, toasted meringue top and bright citrus filling is a stunning family dessert. This elegant classic delivers refreshing flavor in every beautiful slice.
Preheat your oven to 350°F. Place the pre-baked pie crust on a baking sheet for easy handling.
In a saucepan over medium heat, whisk together 1 cup of sugar, cornstarch, salt, and water. Stir constantly until the mixture thickens and starts to bubble, about 6–8 minutes.
In a medium bowl, slowly whisk a small amount of the hot mixture into the beaten egg yolks to temper, then pour back into the saucepan. Stir vigorously over low heat until the filling thickens, about 4 minutes. Remove from heat and immediately stir in lemon juice, zest, and butter until smooth. Pour the warm lemon filling into the pre-baked pie crust.
In a clean bowl, beat egg whites and cream of tartar on medium speed until soft peaks form. Gradually add the remaining 1/2 cup sugar, continuing to beat until glossy stiff peaks form. Mix in vanilla extract.
Spread the meringue over the hot lemon filling, fully sealing the edges to the crust to prevent shrinking. Use a spatula to create decorative peaks. Bake for 18–20 minutes, watching closely, until the meringue is golden brown. Cool completely to room temperature before slicing for the cleanest cuts.