Place the apples for the sauce in a saucepan with a tablespoon of water. Cook on medium heat with the lid on, until soft and tender (about 10 minutes, depending on your apples). Puree until smooth with an immersion blender.
Preheat the oven to 180°C (350°F).
In a mixing bowl, combine the oil and the sugar, then add the applesauce and whisk in the baking soda. It will fizz up at this point.
Next mix in the flour and spices until you have a light, but quite thick batter.
Gently fold in the diced apple chunks, but don't overmix.
Transfer the batter into a 8 inch/20cm greased springform tin, and level out the top with a spatula.
Nut streusel topping
For the topping, combine the finely chopped walnuts, demerara sugar, flour, cinnamon and vegan butter. I often use my fingertips for this, but you can also just give it a good mix with a spatula.
Cover the cake batter with the streusel topping, and gently firm it down all over the cake.
Baking the cake
Bake in a preheated oven at 180°C (350°F) for 40-50 minutes.
To test if the cake is done, insert a cake tester, toothpick or skewer into its center. If it comes out clean, without batter stuck to it, it is done. Keep in mind that there are apple chunks, so it will retain more moisture than other cakes.
When ready to serve, remove the cake from the tin by running a knife around the edge of the cake, release the springform, gently loosen the cake from the base and slide onto a serving plate.
ApplesWe used Bramley apples. We chose not to peel them, but you can if you prefer. If you don't have a blender, then peel the apples for the sauce and mash to a puree with a fork. Instead of making the applesauce fresh, you can use 1 ½ cups or 375g of sugar free canned or store bought applesauce.