Make the Crust and Topping:

1. Preheat the oven to 350ºF and lightly grease an 8×8 inch baking dish.
2. In the bowl of a food processor, pulse together the almond flour, tapioca starch, coconut sugar, vanilla, and salt.
3. Add the butter and pulse a few times to start breaking it up. Turn it on for a few seconds, until the butter is incorporated as coarse crumbs.
4. Add the egg and turn it on once more, until it just starts to come together.
5. Press half the mixture into the prepared baking dish. Transfer the rest to a bowl and refrigerate both the baking dish and the bowl, while you prepare the apples.

Meanwhile, prepare the apples:

1. Peel and core the apples and slice them about 1/8-inch thick.
2. in a large bowl, mix together the apples, coconut sugar, tapioca starch, lemon juice, and cinnamon. Toss with your hands until all the apple slices are well coated.
3. Remove the baking dish from the fridge and dump in the apples. Spread them out so they’re somewhat uniform. Crumble the dough you set aside on top, doing your best to cover as much of the apples as possible.
4. Bake for 55-70 minutes, or until the top is deep golden brown and the apples are tender (I poked them with a toothpick so see how much give they had) If the top starts to get too brown before the apples are tender, cover loosely with aluminum foil.
5. Allow to cool completely in the pan set on a wire rack before cutting into 9 or 12 squares.