Using your smallest pot or saucepan, combine the cornstarch and water. Stirring briskly, bring to a boil until just translucent. Do not overcook. Scrape paste into a small bowl and cover. Set aside.

For the crust: Preheat oven to 400 degrees. Place dough in pie plate and crimp edges as desired. Prick dough several times with a fork. Place a piece of aluminum foil onto the dough and pour in about a cup of dried beans; this will keep the crust from bulging while baking. Bake for 7 minutes, then remove foil and beans and continue baking for 5 minutes. Place crust on wire rack to cool. Reduce oven to 350 degrees.

For the filling: Grate the zest from two lemons to measure 2 to 3 teaspoons. Squeeze lemons to make ½ cup juice. Separate eggs, placing yolks in a small bowl and the whites in the bowl of a mixer.

In a medium saucepan, whisk together sugar, cornstarch, salt and water. Over medium heat, and stirring constantly, heat mixture until very thick, about 2 to 3 minutes. Remove from heat.

Whisk lemon juice into the egg yolks. Carefully add a spoonful of the hot filling to the yolks, immediately whisking to combine. Repeat with 2 more spoonfuls. Then, whisking constantly, slowly pour the egg yolk mixture back into the filling. Return to medium heat and cook until very thick, stirring constantly. Remove from heat. Stir in butter and lemon zest. Set aside.

For the meringue: Mix egg whites and cream of tartar on medium speed until very frothy, about a minute. Slowly begin adding the sugar, a spoonful at a time. It should take you about 2 minutes to add all the sugar. Increase speed and continue beating until whites hold stiff peaks. Reduce speed to low. Add vanilla, and the cornstarch paste, 1 tablespoon at a time. Return to medium speed for about 30 seconds.

Pour filling into the pie shell. Spoon dollops of meringue around the edge, making sure there are no gaps between the crust and the meringue. Pile the remaining meringue onto the filling. Create a few curlicues by dipping the back of a spoon into the meringue and pulling up to create a curl. Don’t overwork.

Bake pie for 15 to 20 minutes, or until meringue is light brown. Let cool completely on wire rack, then refrigerate.