For the topping:
For the cake:
1. Preheat oven to 350F (175C). Grease a 9-inch (23cm) springform pan.
2. In a small bowl stir melted butter, brown sugar and vanilla. Transfer to the prepared pan. Arrange banana rounds on top of brown sugar mixture.
3. Make the cake: in a bowl, stir flour, baking powder, baking soda, cinnamon and salt, set aside. Stir until incorporated. In a separate large bowl mash bananas, add eggs, milk, oil, vanilla extract and sugar. Whisk until combined. add flour mixture and stir until combined.
4. Pour the batter over the banana and caramel layer, bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.
5. Remove from the oven, allow to cool 5 minutes, turn out onto serving platter. Let cool slightly before serving.