Mash the bananas. Place the bananas, eggs, oats, oil, maple syrup, vanilla, baking soda, baking powder, cinnamon and kosher salt in a blender. Blend everything on high for a minute or two until a smooth batter forms.
Add the blueberries to the blender; gently stir until combined.
Place 12 muffin cups into a muffin tin and pour the batter divided evenly between the cups. Sprinkle the tops with turbinado sugar (or extra oats and gently press them down).
Bake for about 30 to 35 minutes until a toothpick comes out clean. Remove from the muffin tin and allow them to cool a few minutes before serving. Store refrigerated or frozen.