Feed your starter early so it is active by mixing time. Let it double.

Mix flour and water until no dry flour remains. Rest for 30–45 minutes to help gluten form.

Add the active starter, sugar, and salt to the autolysed mix. Mix until combined. Use a gentle fold or knead until the dough is smooth but not tight.

Let the dough rest at room temperature for 3–4 hours. Every 30 minutes for the first 2 hours do a set of coil folds or stretch-and-folds to build strength.

Gently spread the dough on a lightly floured surface. Scatter lemon zest and blueberries over the dough. Fold the dough over them and roll or fold a few times to distribute the fruit without smashing it. Finish bulk fermentation until the dough rises about 30–50% and feels airy.

Shape the dough into a tight boule or batard. Place it in a floured banneton or bowl. Cover and put in the fridge for 12–18 hours.

Preheat your oven to 230°C (450°F) with a Dutch oven inside. Take the dough from the fridge, turn it onto baking paper, and score the top with a sharp blade.

Place the dough in the hot Dutch oven. Bake covered for 20 minutes. Remove the lid and bake 15–25 minutes more until the crust is deep golden.

Cool on a rack for at least 1 hour before slicing.