Line a 9×5 inch loaf pan with parchment paper then grease with non-stick cooking spray or butter. Preheat the oven to 350 degrees.
Add the bananas, eggs, maple syrup and vanilla to the bowl of a blender or food processor and blend until smooth. Alternatively, you can mash them up by hand or use an immersion blender. Mix in almond butter, then add the coconut flour, baking powder, cinnamon and salt. Blend or whisk until totally smooth, then pour into the loaf pan.
Make the pecan streusel topping by mixing together the coconut sugar, almond flour, cinnamon and pecans in a medium bowl. Add the butter or coconut oil and use your fingers to blend it into the dry ingredients until it forms coarse crumbles. Sprinkle evenly over the batter.
Bake for 45 minutes to 1 hour, or until a toothpick inserted in the center comes out clean.
Let rest for at least 10 minutes, then use the parchment paper to lift the banana bread out of the pan. Allow to cool for another 10 minutes before slicing, but it will slice better once fully cooled (and even better when cold). Store in the refrigerator.