In a large bowl, whisk together the starter, pumpkin puree, water, and maple syrup until smooth.

Add the bread flour and salt. Mix by hand until no dry flour remains. The dough will be sticky and shaggy.

Cover and rest for 30 minutes.

After the rest, perform the first set of stretch and folds: with damp hands, grab one side of the dough, stretch it upward, and fold it over the center.

Rotate the bowl and repeat on all four sides.

Cover and rest 30 minutes.

Repeat stretch and folds 2–3 more times, every 30 minutes, until the dough feels smoother and more elastic.

After the final fold, cover and let the dough bulk ferment at room temperature until puffy and nearly doubled, about 3–4 hours depending on temperature.

Turn the dough out onto a lightly floured surface and gently stretch it into a wide rectangle.

Sprinkle about half of the cinnamon sugar mixture evenly over the dough.

Fold the dough like a letter and bring the right side over the center, then fold the left side over the top to fully close.

Brush the top with a thin layer of melted butter and sprinkle on the remaining cinnamon sugar mixture.

Starting from a short end, roll the dough up into a snug log.

Pinch the seam well to seal, making sure no filling leaks out.

Gently shape the log into a round boule using light push-and-pull motions. Don’t overwork it. Too much shaping can tear the dough and cause the cinnamon sugar mixture to leak. Don’t worry about it being perfect; the rustic look is perfect for this bread.

Place the loaf seam-side up into a well-floured banneton. Cover and refrigerate overnight (8–12 hours).

The next day, preheat a Dutch oven at 450°F (232°C) for at least 30 minutes.

Remove the banneton from the fridge. Turn the dough out onto parchment paper, seam-side down.

Score the top gently — avoid going too deep so the cinnamon sugar doesn’t leak out excessively. Some bubbling or caramelization is normal.

Carefully transfer the dough into the hot Dutch oven.

Cover and bake for 30–35 minutes.

Remove the lid, reduce the oven temperature to 400°F (204°C), and bake another 10–15 minutes, until the crust is golden brown and the internal temperature reaches about 205°F.

Transfer to a wire rack and cool completely before slicing to allow the crumb and swirl to set.