Preheat the oven to 350 degrees Fahrenheit. Spray a 9×5” loaf pan with cooking spray and line one way with parchment paper for easy removal later.
In a medium-sized bowl, whisk together the sorghum flour, oat flour, erythritol, baking powder, cinnamon and salt.
In an electric stand mixer bowl fitted with a whisk attachment, add the almond milk, mashed bananas, nut butter, eggs, vanilla extract and stevia extract. Mix on low speed.
Add the dry ingredients to the stand mixer and increase the mixer speed to medium. Mix until the ingredients are fully incorporated. Scrape down the sides of the bowl if necessary.
Pour half of the batter into another bowl. Whisk the cocoa powder into one bowl.
Alternate scooping each batter into the prepared loaf pan, and use a knife to swirl the two in order to create the marbled effect. Bake for ~1 hour + 20 minutes, or until the surface forms a light crust and springs back when tapped.
Let cool in the pan for 1 hour, then transfer the loaf to a wire cooling rack to cool completely. Slice and serve, or store in a tightly sealed container in the fridge for up to 4 days.