Prep the oven — Preheat to 375°F and line a muffin pan with liners (or grease well).
Mash the bananas — In a large bowl, mash the overripe bananas until mostly smooth.
Mix wet ingredients — Add melted butter and sugar to the mashed bananas; stir until well combined.
Add dry ingredients — Sift in flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Gently fold until just combined—don’t overmix!
Portion batter — Divide evenly into the muffin cups (makes about 12 muffins).
Bake — Bake at 375°F for 18-20 minutes, or until a toothpick comes out clean.
Cool & enjoy — Let cool slightly before serving warm.
Notes
Don’t overmix — A few lumps in the batter are perfectly fine; it helps keep the muffins tender.
Use very ripe bananas — The spottier the banana, the better the flavor.
Watch the bake time — Every oven is different; start checking at 18 minutes.
Melt the butter (or heat oil) and cool slightly before adding bananas so you don’t cook the banana mash.
If using add-ins (nuts, chocolate chips, fruit), fold them in last and gently so they’re evenly distributed.
Muffin cups should be about ⅔ full; too much batter = muffin domes that crack excessively or longer bake times.
Bake on the centre rack of your oven and rotate the pan halfway if your oven has hot spots.
To test doneness: top should feel set, edges slightly pulling from liner, toothpick in centre comes out clean or with a few moist crumbs (not raw batter).
Cool 5 minutes in pan, then transfer to wire rack—letting them sit longer in the tin can lead to soggy bottoms.
To freeze: once cooled, wrap each muffin individually or pack in freezer bag with parchment layers. Thaw at room temp or lightly warm for best texture.