Buttery crust layered with cinnamon apple filling and topped with light and airy meringue
In a bowl of a standing mixer, beat the sugar, butter, corn syrup or honey, and salt until light and smooth, 4-5 minutes.
Scrap the sides and bottom of the bowl and on low speed, add the beaten egg. Mix until fully incorporated.
Add the flour 1/2 cup at a time, following the vanilla. Mix until you have a soft, smooth dough.
Wrap the dough with plastic wrap and refrigerate overnight. Remove from the refrigerator 10-15 minutes before baking.
Peel and slice the apples into 1/8" cubes, place in a bowl, and sprinkle the lemon juice.
Place the apples and water in a pan over the stove, medium heat. Once it starts to boil, reduce to simmer and let cook for 3-4 minutes.
Place the apples in a bowl, leaving the liquid in the pan.
Add the sugar and cinnamon to the pan with the liquid and stir until the sugar dissolves.
Mix the potato starch with 1/4 cup water and add it to the pan. Once thickened add apples and blend.
Stir and remove from heat.
Place the egg whites and salt in a bowl of a standing mixer fitted with the whisk attachment.
Gradually increase speed to high and beat until frothy.
Reduce heat to low-medium and slowly sprinkle the sugar. Return speed to high.
Beat until you have a shiny firm meringue. 4-5 minutes.
Preheat oven to 350F line a 9", or 9x13-inch for a thinner crust, baking pan with parchment paper, and grease the sides.
Roll the dough and flatten it evenly inside the baking pan. Using a fork, prick it thoroughly and bake it for 22-25 minutes for a 9-inch or 12-14 minutes for a 13x9-inch pan. Until the sides of the crust are starting to lightly brown.
Remove from oven and let cool in the pan for 15-20 minutes. Make the meringue at this point.
Evenly spread the apple filling on top of the baked crust and top it with the meringue. Sprinkle the almonds and return to the oven to bake.
Bake for 15-20 minutes, until the meringue is evenly golden on top.
Remove from oven and let cool completely before slicing.