Preheat oven to 425 F. Use paper liners in a 12-count muffin pan. Mix flour, baking powder, soda, salt, and cinnamon in a medium basin. Set aside.
Place peeled overripe bananas on a plate. Fork-mash them. Set aside. Mix brown sugar and room-temperature butter in a large bowl.
Whisk in eggs, vanilla, and mashed bananas. Stir in the dry ingredients with a spatula until barely mixed and few flour streaks remain. Do not overmix.
Bake 8 minutes at 425 F. After 8 minutes, lower heat to 350 F. (Reduce temperature and bake without opening oven door).
– Serving: 1muffin – Calories: 186kcal – Carbohydrates: 21g – Protein: 2g – Fat: 11g – Saturated Fat: 3g – Polyunsaturated Fat: 4g – Monounsaturated Fat: 3g – Trans Fat: 0.05g – Cholesterol: 16mg – Sodium: 204mg – Potassium: 85mg – Fiber: 1g – Sugar: 11g – Vitamin A: 27IU – Vitamin C: 0.003mg – Calcium: 41mg – Iron: 2mg