Make the walnut crumble topping first. In a small bowl, combine all ingredients and set aside.
In a large bowl, combine oil, maple syrup, coconut sugar and applesauce. Stir well.
Add the eggs and beat until well combined.
In a medium bowl, combine the finely ground almond flour, coconut flour, baking soda and spices.
Add the dry ingredients to the wet ingredients and stir just until combined. Gently fold in the apples.
Spread in prepared pan. Top with walnut crumble.
Bake at 325°F. for 45 - 50 minutes.
Let cool completely. Drizzle with a simple glaze made by combining ½ cup powdered sugar with 2 teaspoons lemon juice, if desired. Good, but not essential. The cake is delicious with or without the drizzle.
Cover any leftover cake tightly or store it in an airtight container in the fridge for up to five days. For longer storage, freeze it for up to three months.