Preheat oven to 350F. Lightly spray muffin tin or paper cups to prevent sticking and set aside. In a large bowl, whisk flour, sugar, baking powder and salt together and set aside. Mash the banana really well using a fork or potato masher and set aside. Juice oranges (about 4 small oranges) and zest one of the rinds. Make a well in the flour mixture and pour in all remaining ingredients. Stir until just combined. Spoon batter into cups 3/4 full and bake 15-25 minutes, until a tooth pick inserted comes out clean (bake time varies on cranberry size and their natural moisture). Immediately transfer muffins to a wire rack and allow to cool.