Preheat the oven to 350 degrees F. and lightly spray a 9x5 inch bread pan with cooking spray.

In a medium mixing bowl, add the mashed bananas and mash with a fork or pastry cutter if not already mashed.

Add the sugar to the bananas and stir well to combine.

Add the sourdough starter, egg, oil, and vanilla. Mix thoroughly.

Add the flour, baking powder, and salt. Fold until just combined and no dry spots remain.

Pour the batter into the prepared bread pan.

Bake for about 60 minutes, or until a toothpick inserted into the center comes out clean.

Cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

Store leftovers in an airtight container at room temperature for 2-3 days or refrigerate for up to a week.