In a large bowl, combine sourdough starter, water, and honey. Stir to dissolve. Add bread flour and mix until a shaggy dough forms. Cover and rest for 45 minutes (autolyse).

Sprinkle salt over the dough. Mix using wet hands or a stand mixer until fully incorporated. Gently fold in blueberries and lemon zest (if using) to avoid bursting the fruit.

Let the dough rise at room temperature for 4–6 hours, performing stretch and folds every 30 minutes during the first 2 hours. The dough should become smoother and puffier.

Turn dough onto a lightly floured surface. Shape it into a round or oval loaf. Place in a proofing basket or bowl lined with a floured towel.

Cover and refrigerate the dough for 6–12 hours. This step deepens the flavor and strengthens the structure.

Preheat your oven to 475°F (245°C) with a Dutch oven inside. Once hot, place the dough into the Dutch oven (score the top if desired), cover, and bake for 20 minutes. Remove lid and bake for another 20–25 minutes until golden brown.

Let the bread cool completely on a wire rack before slicing to allow the crumb to set.