Preheat the oven to 350F and grease a 9×5 loaf pan (8×4 might work too).
Blend mashed bananas, eggs, yogurt, oil, maple, vanilla extract in a food processor/blender/hand mixer or mix by hand thoroughly.
Whisk together flour, salt, cinnamon, baking soda and baking powder.
Combine wet and dry, folding gently until all dry crumbs disappear (do not overmix). Pour half the batter into the loaf pan.
Sift the cocoa powder into the rest of the batter, fold gently until combined.
Pour the rest of the batter into the pan. You can up the marble game by doing alternating scoops of batter, but I was lazy.
Bake for about 60-75 minutes until a thin knife comes out mostly clean with just a few crumbs attached.
Cool in the pan for 15 minutes, turn it out onto a rack to cool completely. Slice and enjoy!