Preheat your oven to 180°C. Grease and line a 20cm cake tin.
Prepare the pie crust first.
Add the tapioca flour, buckwheat flour, brown rice flour, almond meal, coconut palm sugar, sea salt and lemon zest to a bowl. Mix until combined.
Add the cubes of butter and rub the butter into the flour mixture using your fingertips.
In a separate bowl add 2 eggs and beat them. Add 1 ½ eggs to the flour and butter crumb mixture and save the remaining ½ egg.
Mix together well until a dough forms, cover and pop in the fridge to firm up.
Peel the apples, cut them into quarters, remove the core and slice each quarter into 3 further pieces. You should end up with 800g of peeled and sliced apples.
Add the apples to a large mixing bowl along with the cinnamon, coconut palm sugar and tapioca flour.
Mix until the apples are well coated and set aside.
Remove the pastry dough from the fridge, remove ¼ of the dough and set aside.
Dust your surface with flour and roll out the remaining ¾ dough until it’s 1.5 cm thick.
Carefully transfer the dough to the cake tin and press it into the base and up around the sides. Don’t worry if the dough breaks just press it back into place. Make sure the dough lining the cake tin is approx. 1 cm thick in the base and up around the sides.
Sprinkle the 3 tbs of almond meal across the base of the pastry.
Place all of the sliced apples into the pastry shell, the mixture should reach right up to the top of the cake tin.
Take the ¼ pastry dough, dust the surface with flour again and roll out the dough until it’s 1cm thick.
Transfer the dough onto the top of the apple filling and pastry shell. Using your fingertips pinch the edges together.
Brush the top with the remaining egg wash.
Bake in the oven for 1 ¼ hours.
Check the pastry after 45 min and if it’s browning too quickly cover with tin foil.
Remove the tart from the oven and allow to cool completely in the tin.
Pop in the fridge and allow to cool further before serving, this allows the mixture inside the tart to settle.