Preheat and prep: Preheat the oven to 350°F. Grease a muffin pan well or line with paper liners.
Mix the wet ingredients: In a large bowl, mash the bananas until mostly smooth. Whisk in the applesauce, peanut butter, egg, and vanilla until fully combined.
Add the dry ingredients: Sprinkle the flour, baking powder, baking soda, cinnamon, and salt over the wet mixture. Stir just until no dry streaks remain.Tip: Stop mixing as soon as the batter comes together for the fluffiest muffins.
Fill the pan: Spoon batter into the prepared pan, filling each cup about 3/4 full.
Bake: Bake until the tops spring back lightly when touchedMini muffins: 10–12 minutesStandard muffins: 16–18 minutes Cool: Let cool in the pan for 10 minutes, then transfer to a rack to finish cooling.
