Peel the apples, remove the cores and cut the apples into thin slices. Sprinkle with lemon juice.
Mix all the dry dough ingredients. Add apple sauce, rapeseed oil and water to the dry ingredients and knead the dough well.
Line the cake tin with baking parchment and layer it with two-thirds of the dough. Make sure to pat some dough up the sides.
Distribute the apples slices evenly on the dough and sprinkle with cinnamon.
Coarsely grind the whole hemp seeds and mix up with the remaining dough to make the crumble topping. Sprinkle over apples in small chunks until completely covered.
Bake the cake on the middle rack in a fan oven at 160° C (320° F) for about 40 to 45 minutes. You might need to place the cake on the lower rack after 20 minutes if the top gets too dark – so make sure to check regularly.
You can store the cake for a couple of days in an airtight container, but the crumbles won’t be as crunchy anymore as on the first day.