Preheat oven to 350°
Line a muffin pan with paper liners or spray the muffin pan with a baking spray.
In a medium bowl whisk flour, baking powder, baking soda, and salt together.
Add in the banana, oil, eggs, and sugar until blended.
Stir in the cranberries until well combined. (leave some cranberries out if you want to place some on top of the muffins)
Place 3 tablespoons of batter into each muffin pan compartment.
Bake muffins for 20-35 minutes bake until a toothpick comes out clean.
Allow muffins to cool for 5 minutes in the pan, then remove from the pan.
Allow muffins to cool completely.
In a small bowl mix powdered sugar with warm water until the desired consistency, (start with 1 tablespoon water and add a little more at a time, don't add all the water if you don't want it thin).
Drizzle icing over muffins.