Preheat oven at 180ºC / 350ºF. Grease a donut pan with butter or cooking spray.
In a large bowl, mix flour, sugar and baking powder.Add eggs, oil and vanilla. Mix well to combine. Add mashed bananas and mix to combine.
Pour into the donut pan and bake for about 12-15 minutes, or until a knife inserted in the center comes out clean.
For Coating: In a small bowl, mix together the sugar and cinnamon until well combined. While the donuts are still warm, dip each one into the sugar-cinnamon mixture, making sure to coat it evenly on all sides, and enjoy!