In a large mixing bowl, whisk together the sourdough starter, lukewarm water, lemon juice, lemon zest, sugar, and bread flour until combined. Mix until a shaggy dough forms. Cover and let rest for 30-45 minutes (autolyse).

Sprinkle the salt over the dough and gently press it in. Now, begin the stretch-and-fold method:

Wet your hands slightly to prevent sticking.

Grab one side of the dough, stretch it upward, and then fold it over the center.

Rotate the bowl 90 degrees and repeat. Do this a total of 4 times (one full round).

Gently fold in the blueberries during the second round of stretch-and-folds, ensuring even distribution without deflating the dough.

Cover the bowl and let the dough rise at room temperature (21-23°C/70-75°F) for 4-6 hours, performing 3-4 additional sets of stretch-and-folds every 30 minutes during the first 2 hours.

Lightly flour a work surface and shape the dough into a round or oval loaf. Place it seam-side up in a well-floured banneton or a bowl lined with a floured kitchen towel.

Cover the dough and refrigerate overnight (8-12 hours) for enhanced flavor and structure.

The next day, preheat the oven to 450°F (232°C) for at least 30 minutes, placing a Dutch oven inside. Cut a piece of parchment paper or prepare a bread sling to prevent inclusions from sticking and burning.

Remove the dough from the fridge, place it onto parchment paper, and score the top with a sharp knife or bread lame. Carefully place it into the hot Dutch oven.

Bake the bread covered with the lid of the Dutch oven at 450°F (232°C) for 30 minutes.

Remove the lid and bake for another 30 minutes until golden brown.

Transfer to a wire rack and let cool completely before slicing (about 1 hour).