The filling for a lemon meringue pie includes a sugar mixture of two zested and juiced lemons, 1 cup of sugar, 2 tablespoons of all-purpose flour, 3 tablespoons of cornstarch and 1/4 teaspoon of salt. Bakers combine this mixture with 2 tablespoons of butter and four beaten egg yolks, before pouring it into a pre-baked pastry shell to create the base of the pie.
To make the filling for a lemon meringue pie, start by whisking the sugar, flour cornstarch and salt together in a saucepan. Then, stir in 1 1/2 cups of water, the lemon juice and the lemon zest. Bring the stove up to medium high heat, stirring the mixture until it comes to a boil. Once it is boiling, stir in the butter. Beat the egg yolks in a separate bowl, and slowly whisk 1/2 cup of the hot sugar mixture from the saucepan into them. Then, slowly whisk this mixture back into the remaining hot sugar mixture in the sauce pan. Bring the saucepan back to a boil, and stir it occasionally, cooking it until the filling thickens.
To finish the pie, make meringue in a large bowl. Start by whipping four egg whites until they are foamy. Gradually whip in sugar, continuing to do so until the mixture thickens and begins to form peaks. Spread this mixture over the lemon filling in the pre-baked shell, and bake in a preheated, 350 degree Fahrenheit oven for 10 minutes or until the meringue is golden brown.