In a large bowl, mix the melted butter, sour cream (or plain yogurt) and sugar by hand, with a wooden spoon. Beat until blended, then add the eggs one at a time. Mix well.
Add the flour mixture, a third at a time, stirring well with the wooden spoon after each batch. Transfer the batter into a 9x5-inch loaf tin and bake in the middle of the oven for 60 - 75 minutes.
Insert a toothpick, fine skewer or a cake tester in the center of the banana bread. It should come out clean. Leave in the tin on a rack to cool, about 30 minutes.
The ultimate and super moist banana bread with rum. This moist banana bread recipe is easy, healthy, made with overripe bananas, sour cream and brown sugar!