Make the chia eggs by mixing together 2 Tbsp of ground chia seeds with 6 Tbsp of water. Set aside.
Line the bottom of a springform cake tin ( ⌀ 23cm / 9in) with baking sheet. Grease well all over.
In the bowl of a food processor mix together the flour, baking powder, baking soda, salt, cinnamon and 200g of golden caster sugar.
Mash the banana. Mix in a bowl with the vegetable oil and vanilla. Set aside.
Peel and core the apples. Cut into thin slices.
Mix the banana mixture in the flour, followed by the chia eggs and the almong milk.
With a wooden spoon, gently mix the apple slices in the cake batter.
Pour the cake batter into the cake tin. Spread evenly.
Cook in the oven for 30 mins.
5 mins before the end, melt the dairy-free butter in a saucepan. Add the sugar and almond flakes. Mix well together.
When the cake is ready, spread the almond mixture evenly on top of cake.
Return the apple cake to the oven for another 10 mins until top is golden and crisp and an inserted cake skewer comes out clean.
Leave the cake to cool down in its tin then carefully remove sides of the spring form cake pan. Run a palette or rounded knife on the inside edge of the cake pan first to make sure the cake comes out neatly. Cool completely.