HEAT oven to 325°F. FILLING: MIX sugar, cornstarch and salt in large heavy saucepan. Gradually STIR IN water and lemon juice until smooth. ADD egg yolks; stir until blended. ADD butter.
COOK over medium heat, stirring constantly, until mixture thickens and comes to a boil. REDUCE HEAT; SIMMER, STIRRING constantly, 1 minute. REMOVE from heat. STIR IN lemon peel.
Immediately make MERINGUE: DISSOLVE cornstarch in cold water in one-cup glass measure. MICROWAVE on HIGH 30 seconds; STIR. MICROWAVE until mixture boils, 15 to 30 seconds longer. REMOVE; COVER.
BEAT egg whites and cream of tartar in mixer bowl with whisk attachment on high speed until foamy. Beating constantly, ADD sugar, 1 Tbsp. at a time, beating after each addition until sugar is dissolved before adding the next. Continue beating until whites are glossy and stand in soft peaks. Beating constantly, ADD cornstarch paste, 1 to 2 Tbsp. at a time. BEAT in vanilla.
POUR hot filling into pie crust. Quickly SPREAD meringue evenly over filling, starting at edge and sealing to crust all around; swirl with back of spoon. BAKE in upper third of 325°F oven until lightly browned, 16 to 18 minutes. COOL on wire rack 30 minutes to 1 hour.
Serve freshly made pie at room temperature, or refrigerate, uncovered. Garnish with lemon peel twists and fresh mint.
A hot filling is important. The heat of the filling cooks the bottom of the meringue and prevents it from weeping and creating a slippery layer between filling and topping. Set up your equipment and measure meringue ingredients before you make the filling and work quickly to make meringue before filling cools.
This recipe is a good source of protein, folate and choline.
Anchor the meringue. Be sure to attach the meringue to the crust all around the edge of the pie. This prevents the meringue from pulling away from the edge during baking.
Refrigerate any leftover pie promptly.
For more detailed meringue techniques and information, see Basic Soft Meringue.