Preheat the oven to 350°F (175°C) and grease a 9x5-inch loaf pan.
In a large mixing bowl, mash the overripe bananas (with a fork) until smooth. Add the melted butter, sugars, and vanilla extract, and orange juice (if using) and mix until combined.
Whisk in the egg, yogurt, and sourdough starter until combined.
Next, in a separate bowl whisk together the flour, baking soda, baking powder, cinnamon, and salt.
Toss the fresh cranberries in the dry flour mixture to coat them evenly. This helps prevent them from sinking to the bottom of the loaf during baking.
Gradually fold the dry ingredients into the wet mixture, mixing just until combined. Be careful not to over mix to ensure a tender loaf.
Then transfer the batter to the prepared loaf pan, spreading it evenly with a spatula.
Place the loaf in the preheated oven and bake for 55-60 minutes, or until a toothpick inserted into the center comes out clean.
Allow the bread to cool in the pan for 10-15 minutes, then transfer it to a wire rack to cool completely before slicing.
Wrap the cooled bread tightly in plastic wrap or aluminum foil and store it at room temperature for up to 3 days.
For longer storage, wrap it well and freeze for up to 3 months. Thaw at room temperature before serving.
Notes
Sourdough discard: ensure your sourdough discard is no more than a few days old as it may make the bread more acidic.