This classic pie recipe is topped with a mile-high meringue that's made with six egg whites--a few more than many recipes use. Perfect for the delicious tart lemon filling.
Heat oven to 425°F. Fit pastry into a 9-inch pie plate. Roll dough under and crimp for fluted edge. Prick crust with fork. Line with foil; fill foil with dried beans or pie weights.
Bake at 425°F. for 12 minutes. Remove foil and beans. Bake 8 minutes or until golden. Cool.
Grate 2 tablespoons rind; set aside. Squeeze 3/4 cup juice from lemons. Mix sugar, cornstarch, salt in saucepan. Stir in 2-1/4 cups water, lemon juice. Cook over medium heat, stirring, 15 to 20 minutes or until thickened and bubbly. Cook another 2 to 3 minutes, stirring. Remove from heat.
Beat yolks lightly in bowl. Stir 1/2 cup hot lemon mixture into yolks, then stir yolk mixture back into full lemon mixture in saucepan. Cook over low heat, stirring, 1 minute (don't overcook). Off heat, add butter and grated lemon rind. Pour into baked crust.
Reduce oven temperature to 325°F.
Beat egg whites and cream of tartar in large bowl until foamy. On high speed, beat in sugar, one tablespoon at a time, until stiff peaks form. Spoon meringue over filling, spreading to edge of crust to seal. Swirl into peaks.
Bake on lower rack at 325°F. for 25 to 30 minutes (thermometer inserted in meringue will register 140°F). Bake 3 minutes longer. Cool on rack up to 2 hours. Refrigerate at least 1 hour before slicing.