Begin the batter 16-18 hours before you plan to bake the cranberry pumpkin bread. This allows the sourdough starter to ferment the flour, enhancing its digestibility and nutrient availability.
In a large bowl, whisk together the flour, baking powder, baking soda, salt, and pumpkin spice.
In another bowl, combine the sourdough starter, sugar, butter or oil, eggs, and pumpkin purée. Mix until well combined.
Add the wet ingredients to the dry ingredients and stir until just combined. Do not overmix.
Stir in the cranberries.
Cover the mixture with a damp kitchen towel or plastic wrap.
For best results, let it ferment at room temperature for 4-6 hours.
Place dough into the fridge for the second rise and let it continue fermenting overnight for an additional 12 hours.
The next morning, after the final rise, preheat your oven to 350°F (175°C).
With a Danish dough whisk or a wooden spoon, give the pumpkin sourdough dough a few good stirs.
Pour the batter into TWO prepared loaf pans and bake for 55-60 minutes. Stick a long toothpick in the center and when it comes out clean it is ready.
Let the sweet bread cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely.