Heat oven to 400 degrees. Mush two prepared pie crusts together to line a 9-inch super deep dish pie plate. Crimp the edges decoratively. In a small bowl, whisk together egg yolk and cream to make a glaze. Prick the bottom of the shell with a fork, brush the top edges with the glaze, and line the bottom with parchment paper. Weight the shell with pie weights or dried beans, and bake until the edges begin to brown, 10 to 15 minutes. Remove paper and weights; continue baking until golden brown, 7 to 10 minutes more. Let cool.
You will need at least 4 9-inch spring-form pans to prepare each layer of the pie separately.
To make the first layer of pie filling, disolve a packet of gelatin in water and bring to a boil over the stove, turn down the heat and then combine 1/3 cup each of cornstarch & cake flour, 1/4 teaspoon of salt, and 1/4 cup sugar over medium heat. Gradually add 1 cups cold water, and bring to a boil again, whisking constantly, about 4 minutes.
Remove the pan from heat. Temper 5 egg yolks by beating a small amount of hot mixture into the yolks before adding them to pan. You do not want them to scramble/curdle. You just want to heat the beaten yolks but keep them in a creamy, liquid form. Cook over low heat for 5 minutes.
Remove the pan from heat, and whisk in the lemon juice and rind. Add the butter one piece at a time. Pour the mixture into a large bowl, and let cool.
Once cooled, pour the filling into a 9 inch spring form pan, covered with aluminum foil, and chill in the refrigerator until firm, at least 2 hours.
Repeat the above steps again, for the second layer of pie, and once completed, pour into another 9-inch springform pan and let chill.
In two additional 9-inch spring form pans, bake two lemon cakes using one half of a box of cake mix (Williams-Sonoma Meyer Lemon Pound Cake Mix) for one pan, and 1/2 the mix for the other pan. Let the cakes cool.
You should now have 4 layers---- 2 springform pans of chilled pie filling, and 2 spring form pans of thin lemon cake. To assemble the pie, start with the pre-cooked crust and sprinkle a dusting of powdered sugar across the bottom of the crust with either a fork or a brush. Then open the spring form pan of pie filling and place on top of the powdered sugar crust. A layer of lemon cake goes on top of that. Then place the second pie filling layer on top of that. You want to end up with a layer of cake on the very top, and the meringue topping will sit on that top layer of cake.
To make the meringue, pour the egg whites and creme of tartar into a very clean and dry copper or stainless steal mixing bowl. Beat on a low speed with an electric mixer. Gradually add in the salt and extra-fine sugar, but very very slowly, and gradually turn up the speed of the mixer. You want the egg white to beat till they form soft shiny frothy peaks, but not so stiff that they aren't flexible enough to swirl. Add the Vanilla at the very last moment. With a rubber spatula, swirl the beaten meringue into a 9-inch spring form pan, covering the entire perimeter of the pan and bake for 6 minutes or until lightly brown.
Let the Meringue topping cool for at least a half hour, then undo the spring form pan and place on top of the other cake/pie layers.