Preheat the oven to 350°F. Grease the bottom of a loaf pan with coconut oil, and line it with a piece of parchment paper. Cut paper to fit lengthwise, leaving some excess on the edges.
Mix together the almond flour, coconut flour, cinnamon, baking soda and salt.
In a separate bowl, whist together the coconut milk, coconut oil, maple syrup, eggs (or flax eggs), apple cider vinegar and vanilla extract.
Using a rubber spatula, mix dry and wet ingredients together just until combined. Do not overmix.
Gently fold into the batter the apple slices and chopped walnuts (reserve about 1 tablespoon of walnuts for the crumb topping).
Pour batter into the prepared loaf pan.
Mix all the crumb topping ingredients together with your hands, then sprinkle top of bread with the crumbs and reserved walnuts.
Bake for 30 minutes, then cover bread with aluminum foil and bake until a toothpick inserted into the center comes out clean, about 20 more minutes. Total baking time should be approximately 50 minutes. Let sit for a few minutes to cool.
Carefully remove bread from the pan while still warm, and drizzle caramel over the top before serving. The recipe serves 8-10 people. Store in the refrigerator.