Beat the butter and sugars with an electric mixer for 8 to 10 minutes or until pale and creamy.
Add the eggs, one at a time and beat well (make sure the egg is well incorporated before adding the next one, or your batter may split).
Add the flour, baking powder and cinnamon and mix well.
Add the sour cream and mashed bananas and stir to combine.
Pour the batter into a greased and floured Bundt pan and bake it in a pre heated oven at 180°C – 350°F for 50 to 60 minutes, or until cooked through (test with a toothpick, it should come out clean).
Allow to cool in the pan for 10 minutes, then turn it out onto a cooling rake to finish cooling.
Maple Caramel Sauce
Put the butter, brown sugar, syrup and cream in a saucepan and cook it over medium heat, stirring, until the sugar dissolves.
Turn the heat up and bring the mixture to a boil, continue cooking on a low boil for 12 to 15 minutes or until it thickens.
Cool to room temperature before pouring it over the cake.