Combine sourdough starter, warm water, and flour in a mixing bowl. Stir until cohesive.

Cover with a damp cloth and let rest for 30 minutes.

After resting, add salt, lemon zest, and lemon juice. Mix until combined.

Cover the bowl and let dough bulk ferment for 4 to 5 hours, performing stretch-and-fold every 30 minutes.

After final stretch-and-fold, gently fold in blueberries and cream cheese.

Shape the dough into a round boule and place seam-side up in a floured proofing basket. Refrigerate for 8 to 12 hours.

Preheat the oven to 475°F with the Dutch oven inside.

Turn the dough onto parchment paper, score the top, and transfer to the Dutch oven.

Cover and bake for 20 minutes. Remove the lid and bake for another 20-25 minutes until golden brown.

Transfer to a wire rack to cool completely before slicing.