Step 1: Make the Dough
In a large mixing bowl, whisk together the warm water, sourdough starter, and sugar.
Add the bread flour, salt, melted butter, egg, lemon zest, and lemon juice. Stir until a shaggy dough forms.
Knead by hand (8–10 minutes) or with a stand mixer (6–7 minutes) until smooth, elastic, and slightly tacky (but not sticky).
Step 2: First Rise
Transfer the dough to a lightly oiled bowl, cover with plastic wrap or a damp towel, and let rise in a warm place for 4–5 hours, or until doubled in size.
Step 3: Prepare the Cream Cheese Filling
While the dough rises, beat the softened cream cheese until smooth.
Add the sugar, egg, and vanilla extract, mixing until fully combined. If too thick, let it sit at room temperature to soften.
Step 4: Assemble & Shape
Once risen, turn the dough onto a floured surface and gently press into a rectangle.
Spread the cream cheese filling evenly over the dough, leaving a 1-inch border.
Scatter blueberries over the cream cheese layer.
