Skin and cut the bananas into cubes. In a frying pan, melt the butter and fry the banana cubes until pink. Remove them, drain well and put to one side. In the melted butter that is left over in the saucepan, add the sliced onion. When it starts to brown, add the manioc flour. Stir until it starts to brown. Season with salt and add the banana cubes. Mix and serve as an accompaniment to fish.
Serves 6.