Preheat oven to 350 degrees F (176 C) and line a loaf pan with parchment paper or lightly grease.
Prepare flax egg in a large mixing bowl and let rest for 5 minutes. Then add ripe, peeled banana and mash well with a fork. You want it pretty smooth.
Add almond butter, avocado oil, coconut sugar, maple syrup, sea salt, and almond milk and whisk to combine. Add baking powder, almond meal, gluten-free flour blend, and gluten-free oats and stir well to combine. Lastly, add half of the walnuts and stir to combine.
Pour into the pan and smooth with a spoon. Top with remaining walnuts. Bake for 1 hour to 1 hour 15 minutes. When done, the loaf should feel firm and be crackly and golden brown on top (see photo). A toothpick or knife should come out clean (or with very few crumbs).
Let rest in the pan for 10 minutes, then carefully loosen sides with a knife or pull up on the parchment paper to transfer to a cooling rack. Let cool completely before cutting or it will be tender and tend to crumble. It’s even better the next day!
Store leftovers covered at room temperature for up to 4-5 days. Slice and freeze for up to 1 month. Reheat in the microwave or toaster oven until tender and warmed through.
*If subbing chicken eggs for flax eggs, 1 flax egg generally = 1 small chicken egg. *If not gluten-free, use unbleached all-purpose flour or spelt flour in place of the gluten-free blend.