The starter must be active. To do this, the night before prepare it, by mixing 2 tbsp. sourdough starter with 1/4 cup of water and 1/4 cup of all purpose flour. Set in warm area. By morning, your starter will be bubbly, frothy and active.
In a small bowl, add sourdough starter and remaining water. Mix. Add pumpkin puree. Mix. Add salt and flour together and then pour into your pumpkin mix bowl. Combine until you have your dough.
Cover with plastic wrap and a towel on top of that, set into a warm area and let rest for 30 minutes. Remove dough and sit on very lightly floured surface to stretch and fold each edge of the dough in over the center of itself. Set back into the bowl, covered, in a warm area with a towel on top.
Repeat this procedure 2 more times so it has rested 3 times for 30 minutes and then the last time knead VERY gently so it stays poofier, then leave the dough for 3.5 hours. It should have doubled after all of this, warmer areas will do this faster than cooler spaces.
Put the dough on a lightly sprinkled surface, form a ball and leave for 30 minutes covered gently with a dish towel.
Line a bowl with a kitchen towel sprinkled with flour. Form dough into a ball and place steam side facing up on to the floured towel. Cover the bowl with plastic wrap and put into the fridge overnight.
Set oven to 500 degrees F with your Dutch oven in it to heat up. Remove your dough from fridge. Set on a piece of parchment paper. Set inside heated Dutch Oven and cover with the lid. Bake for 20 minutes this way.
Remove lid and continue baking for another 15-20 minutes until there is a nice golden crust all around the loaf. Remove from Dutch Oven and set on cooling rack to cool for 1 hour. Then slice with bread knife.