Using a fork, turn 4 bananas into mashed potatoes. Add eggs, vegetable oil, sugar and cinnamon and mix well. Pour the flour and mix thoroughly until a homogeneous consistency.
In a saucepan over moderate heat, melt the butter. Dissolve brown sugar in it. Increase the heat slightly and cook, stirring until the mixture begins to bubble.
Pour the caramel into a 23 × 23 cm shape. Cut the remaining bananas into circles and place on the caramel. Spread the dough on top. Bake the cake at 180 ° C for 40–50 minutes. Cool it and turn it over to a serving dish.
