In a large bowl, whisk the active sourdough starter into the water until mostly dissolved.

Add the bread flour and salt, mixing until a shaggy dough forms and no dry flour remains.

Cover the bowl and let the dough rest for 45 minutes for autolyse.

Perform four sets of stretch and folds every 30 minutes, folding in the lemon zest and sugar during the first set.

During the final set of folds, gently laminate in the blueberries which have been tossed in the extra tablespoon of flour.

Allow the dough to bulk ferment at room temperature until it has increased in volume by approximately 50-75%.

Gently shape the dough into a boule and place it into a floured banneton.

Cover and place in the refrigerator for a cold retard of 12 to 18 hours.

Preheat a Dutch oven in an oven at 450F (230C) for 45 minutes.

Score the cold dough and carefully transfer it into the hot Dutch oven.

Bake with the lid on for 20 minutes, then remove the lid and bake for an additional 25 minutes until the crust is deep golden brown.

Cool completely on a wire rack for at least 2 hours before slicing.