Preheat your oven to 350°F (175°C) and generously grease your donut pan.

In a mixing bowl, mash the ripe bananas until they are smooth.

Add in the eggs, granulated sugar, milk, and melted butter to the mashed bananas; mix together until well blended.

In a separate bowl, combine the all-purpose flour, baking powder, and ground cinnamon, then gently stir before incorporating it into the wet mixture until just combined.

Fill each cavity of your prepared donut pan about three-quarters full with the batter.

Bake for 10-12 minutes, or until golden brown and a toothpick inserted comes out clean. Allow to cool slightly before transferring to a wire rack.