The primary ingredient in lemon meringue pie is lemon juice, which provides the tart and refreshing flavor that characterizes this classic dessert. The pie consists of a crispy pie crust filled with a lemon-flavored custard made from lemon juice, sugar, cornstarch, and egg yolks. Once the filling is prepared and cooled, it's topped with a light and fluffy meringue made from whipped egg whites and sugar, which is then baked briefly to achieve a golden-brown finish. Lemon meringue pie offers a delightful balance of sweet and tangy flavors, making it a favorite among dessert lovers.