Heat oven to 190C/170C fan/gas 5, and lightly oil a 20cm springform tin and line the base with a circle of baking parchment.
In a stand mixer, or using a hand blender, whizz together the oil and maple syrup for 30 secs. Add the eggs and whizz for another 1 min before adding the apple sauce and blending for a further 30 secs. Tip in the ground almonds, baking powder, 1 tsp salt and cinnamon, blend for 30 secs and your batter is done. Pour it into the tin, and bake for around 30-40 mins or until the top is a deep golden brown, the cake is coming away from the sides a little, and a skewer inserted into the centre comes out clean.
While it’s cooking, make the topping. In a small frying pan, cook the apple gently with the rest of the topping ingredients and ½ tsp salt until the apple is soft and gently caramelised. When the cake is ready, scatter the bronzed apple chunks on top of the cake. You could also make it with chunks of caramelised peach or plum on top, or some cherry compote, or any berries which you have softened in a pan with a little water and maple syrup. Eat warm, as a pudding, with a spoonful of Greek yogurt, or cold with a cup of tea or coffee.