Preheat oven to 180 degrees C. Spray a 25cm ring tin with non-stick cooking spray.
In a large bowl cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time. Beat in the sliced bananas, sour cream and bicarb soda. Beat in the flour. Pour batter into prepared pan.
Bake in the preheated oven for 60 minutes or until a toothpick inserted into the centre of the cake comes out clean. Let cool in pan for 10 minutes then turn out onto a wire rack and cool completely.