Mix the flour with salt and mix in the coconut oil piece by piece until the mixture becomes slightly crumbly. With the mixer running, add about 4 tablespoons of ice water so that the crumble becomes doughy. Take the dough out of the bowl, shape into 2 plates and wrap in foil and put in a cool place for about 60 minutes.
Then roll out a sheet of dough about 3 mm thick, fold it up and place in the greased springform pan (28 cm). Unfold and form an approx. 3 cm high edge. Whisk the egg white with a little water and coat the bottom and edges with it. Roll out the second sheet of dough slightly larger than the shape.
Preheat the oven to 225 ° C (top / bottom heat, convection: 200 ° C). Wash and peel the apples, remove the core and cut the flesh into wedges. Mix in a bowl with lemon juice, maple syrup, sugar, cornstarch and spices.
Pour the filling on the dough, cover with 1 tablespoon flakes of butter. Place the second sheet of pastry on top and press firmly. Brush with the remaining flakes. Poke a few holes in the lid to allow the steam to escape.
Bake for about 10 minutes. Then reduce the temperature to 180 ° C (convection 160 ° C) and bake the cake for another 40-45 minutes.