Prep the pan and oven: Preheat oven to 350°F (175°C). Line a 12-cup muffin pan with paper liners or lightly grease with oil.
Mash the bananas: In a large bowl, mash bananas with a fork until mostly smooth.
A few small lumps are fine.
Whisk in wet ingredients: Add egg, yogurt, oil, maple syrup or honey, and vanilla. Whisk until well combined and creamy.
Combine dry ingredients: In the same bowl, sprinkle flour, baking soda, baking powder, cinnamon, and salt over the wet mixture. If using flax or chia, add now.
Mix gently: Stir with a spatula just until no dry spots remain. Do not overmix; a slightly lumpy batter keeps cupcakes tender.
Add fruit (optional): Fold in mini blueberries or finely chopped soft fruit.
Pat fruit dry first to avoid soggy spots.
Fill the cups: Divide batter evenly among muffin cups, filling each about 3/4 full.
Bake: Bake 14–18 minutes, until the tops are set and a toothpick comes out clean or with a few moist crumbs.
Cool: Let cupcakes cool in the pan for 5 minutes, then transfer to a rack to cool completely. This keeps the texture light and prevents sogginess.
Serve: Enjoy plain or top with a small dollop of lightly sweetened yogurt. For toddlers, cut into halves or quarters if needed.