Prep the pan and oven. Heat the oven to 350°F (175°C).
Line a 12-cup muffin pan with liners or grease well.
Mash the bananas. In a large bowl, mash the bananas until mostly smooth. A few small lumps are fine.
Whisk in wet ingredients. Add eggs, applesauce, maple syrup, oil, and vanilla. Whisk until well combined.
Mix the dry ingredients separately. In another bowl, stir together oats, flour, baking powder, baking soda, cinnamon, and salt.
Combine gently. Add dry ingredients to the wet.
Stir with a spatula until just combined. Do not overmix. Fold in any add-ins.
Portion the batter. Divide evenly among the muffin cups.
Fill each about 3/4 full.
Bake. Bake 16–20 minutes, until the tops are set and a toothpick comes out clean or with a few moist crumbs.
Cool. Let muffins cool in the pan for 5 minutes, then move to a rack. Cool fully for the softest texture.
Serve. Serve plain or with a swipe of nut butter or cream cheese for extra protein and fat.