Make the dough. In a medium bowl, use a fork to whisk together the water, starter, salt, and pumpkin purée until smooth. Add the flour, sage, and pumpkin seeds. Mix together until a rough, shaggy dough forms. Cover with plastic wrap or a damp towel and rest at room temperature for 30 minutes.
Form the dough. After the 30 minute rest, form the dough into a rough ball shape by stretching the four sides of the dough gently up and over the dough one side at a time. How to do the stretch and folds: using a lightly wet hand, pull one side of the dough away from the edge of the dough and gently stretch it up and over the remaining dough, pushing it slightly into the dough. Repeat with the remaining sides. Cover the bowl with plastic wrap or a damp towel. Let the dough rest for 1 hour covered.
Stretch and folds. Repeat the stretch and folds, cover and let the dough rest again for 1 hour, then repeat the stretch and folds one last time.
Bulk rise. After the final stretch and fold series, cover the dough with plastic wrap or a damp towel and let the dough rest another 3 to 4 hours (for a total bulk rise of about 6 hours). Depending on the temperature of your kitchen, this could take more or less time. The dough should look about double in size and have a bit of bounce to it if poked with a finger.
Shape the dough. Generously flour a medium bowl lined with a cotton or linen cloth or use a proofing basket, set aside. Tip the dough from its bowl onto a very lightly floured surface. Gently stretch and fold the four sides of the dough. Using a bench scraper, flip the dough over, cover with a damp cloth and rest 15 to 20 minutes.
With the bench scraper, flip the dough over again so the smooth side is facing the work surface. If the dough is sticky, wet your hands. Cup your hands around the far side of the dough and pull it towards you in a circular motion. You may find it easier to use a bench scraper to help you slightly move the dough while you shape it. After shaping the dough, place it seam side up in the proofing basket/cloth-lined bowl.
Second rise. Let the dough rest for 30 minutes to 1 hour or leave the dough in the fridge overnight. Preheat the oven to 450°F with the dutch oven and lid inside. Cut a piece of parchment paper to fit the inside of your dutch oven with just enough space to lift into the pan. I like to cut a parchment paper circle with narrow, longer pieces of two sides to use as handles.
Make the pumpkin shape. Optional: Sprinkle the top of the loaf in the breadbasket with cornmeal (this will end up being the bottom once the dough is turned out). Cut 4 long pieces of kitchen string and place over the dough in the breadbasket at 12 o'clock, 3 o'clock, in between 4 and 5 o'cloc, and in between 7 and 8 o'clock. Cover with parchment paper, then a cutting board or plate and gently flip over. After turning the dough out, sprinkle and lightly rub flour over the surface of the dough. Tie the strings at the center of the top of the dough. Cut any excess string.
Score the dough. Use your own design to score the dough. To keep the pumpkin shape, don’t score too deep.
Bake the dough. Remove the dutch oven from the oven and remove the lid - remember the lid will be super hot! Carefully place the dough in the dutch oven. Cover with the lid and bake at 450°F for 20 minutes. Remove the lid and reduce the oven temperature to 425°F. Bake for another 45 minutes until the center of the loaf reaches 205°F
Cool the dough. Carefully remove the dough from the dutch oven and let cool on a wire rack or cutting board for 1 hour before cutting for the best texture. Cut and remove the kitchen string. Add an inverted cashew or piece of cinnamon stick to the center of the dough for the stem of the pumpkin. Slice and serve!