Preheat oven to 350 degrees F (180 degrees C). Grease the sides of an 8 or 9-inch springform pan with coconut oil and line the bottom with parchment paper.
Combine Zucchini (1 cup), Apple Sauce (1/2 cup), Egg (2), Banana (1), Dark Pure Maple Syrup (1/2 cup), Vanilla Extract (1 teaspoon), and Coconut Oil (1/2 cup) in a large bowl.
Combine Brown Rice Flour (1 cup), Coconut Flour (1/2 cup), Baking Powder (1 teaspoon), Ground Nutmeg (1/2 teaspoon), and Ground Cinnamon (1 teaspoon) in a separate bowl.
Combine dry and wet ingredients together. Fold in the Walnut (1/4 cup).
Pour cake mixture into a springform pan and sprinkle additional walnuts on top. Place in oven and bake for 25-35 minutes until a knife inserted comes out clean.
Let cool slightly, then slice and serve.