1. Feed sourdough starter 8-12 hours before baking until doubled and bubbly.

2. Mix bread flour and water in a large bowl until no dry flour remains. Cover and rest for 30 minutes (autolyse).

3. Add bubbly starter, honey, and lemon zest. Mix with wet hands for 2-3 minutes until incorporated.

4. Add salt and mix for 2 more minutes. Cover and begin bulk fermentation.

5. Perform stretch and folds every 30 minutes for the first 2 hours (4 folds per session).

6. Let dough rest undisturbed for 2-3 more hours until increased by 50-75% with visible bubbles.

7. Toss blueberries with cornstarch. Gently fold berries into the dough.

8. Pre-shape dough into a round. Rest for 20 minutes.

9. Mix softened cream cheese with honey, lemon juice, and vanilla until smooth.

10. Roll dough into a 10×14-inch rectangle. Spread cream cheese mixture over surface, leaving a 1-inch border.

11. Roll dough tightly from the short end like a jelly roll. Pinch seam closed.

12. Place seam-side down in a parchment-lined 9×5-inch loaf pan. Cover tightly.

13. Refrigerate for 8-16 hours for cold fermentation.

14. Preheat oven to 450°F with Dutch oven inside (or place empty roasting pan on bottom rack) for 1 hour.

15. Score the top of the loaf with one long slash down the center, about 1/2 inch deep.

16. Bake covered for 20 minutes (or with steam), then uncovered for 25-30 minutes until internal temperature reaches 205-210°F and crust is deep golden.

17. Remove from pan immediately and cool on wire rack for at least 2 hours before slicing.