Filling: 1 cup sugar 5 tablespoons cornstarch 1/4 teaspoon salt 1 cup water 1/2 cup milk 4 large egg yolks 1 tablespoon unsalted butter 1/2 cup fresh lemon juice 2 teaspoons freshly grated lemon zest 1 Pastry for 9" pie
Meringue: 4 large egg whites 1/4 teaspoon cream of tartar 1/2 cup sugar
Filling: In a heavy saucepan whisk together sugar, cornstarch, and salt and gradually whisk in water and milk, whisking until cornstarch is dissolved. In a bowl whisk together egg yolks. Cook milk mixture over moderate heat, whisking, until it comes to a boil. Gradually whisk about 1 cup milk mixture into yolks and whisk yolk mixture into milk mixture. Simmer mixture, whisking, 3 minutes. Remove pan from heat and whisk in butter, lemon juice, and zest until butter is melted. Cover surface of filling with plastic wrap.
Meringue: In another bowl with an electric mixer beat egg whites with cream of tartar and a pinch of salt until they hold soft peaks. Beat in sugar in a slow stream, beating until meringue just holds stiff peaks.
Pour filling into shell and spread meringue on top, covering filling completely, sealing it to pastry. Draw meringue up into peaks and bake pie in middle of 350 degree oven until meringue is golden, about 15 minutes.
