It's not exactly perfect but this was my first attempt at making a pie with meringue topping. I love Key Lime, so I had to try it. It tastes better than it looks, but I am not sure it is really my favorite rendition. I prefer more of the creamy based key lime, but again, the flavor is on point. This recipe from Kitchenaid called for 1/2 cup of fresh Key Lime juice, 1 tsp of grated lime peel (aka zest), 3 eggs separated, 2 tbsp of butter, 1/4 tsp salt, 1.5 cups of sugar, 1.5 cups boiling water, 1/4 cup of corn starch, and 1/2 cup cold water.
Take sugar, cornstarch, and salt and integrate. Place in 2 qt sauce pan and add lime juice, egg yolks, cold water. Whisk well. Now add 1.5 cups of boiling hot water slowly (no it will not cook the egg yolks). Now add butter. Bring filling to a boil over medium heat and stir continuously for 3 minutes. At the boiling point, the consistency of the filling will change dramatically. Remove from heat, place in a cool container and cool completely. Once it cools, add the lime zest and a tiny, tiny amount of green food coloring. This is optional, but it gives it a nice look and the zest really adds to the flavor.
The easiest part of making the pie turns out to be the meringue, but it's one of those things you can't really make in advance. To make meringue, simply whip 3 egg whites in a stand-up mixer on high until it starts to froth and thicken, then add a dash (1/4 tsp) of cream of tartar, at which point it will quickly begin turning white. Now add 1/2 cup sugar slowly until stiff peaks have formed. It takes only about 3 minutes total and it's as simple as that. Immediately top the cooled pie filling with the meringue being sure to push it to touch the edges of the crust.
Bake the pie at 350 degrees for 13-15 minutes or until the meringue it becomes lightly browned on top. Cool pie completely, slice, and enjoy.