Remove foil and beans and continue baking for 5-10 more minutes. Place crust on wire rack to cool. Reduce oven to 350 degrees.

Using your smallest pot , 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.

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. Place the egg whites in the bowl of a mixer.

In a medium saucepan, whisk together sugar and cornstarch paste. Stir constantly over medium heat. The mixture will become 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.

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.

Spoon dollops of meringue around the edge, making sure there it goes right to the edge of the crust (no gaps).

Pile the remaining meringue onto the filling. With the back of the spoon, create a few wisps.

Bake pie for 15 to 20 minutes, or until meringue is light brown. Keep an eye on the pie. You don’t want it to get too brown. Let pie cool completely on wire rack. Refrigerate and when ready to slice, dip a sharp knife in hot water.