01 - Combine bread flour, sourdough starter, water, and sea salt in a large bowl. Stir until a shaggy, rough dough forms. Cover the bowl and let rest for 30 minutes to hydrate.
02 - Perform 2 to 3 sets of stretch and folds over 1.5 hours, resting the dough for 30 minutes between each set. After the final fold, cover and refrigerate overnight for 8 to 12 hours to develop flavor and structure.
03 - Generously coat a 9x13-inch baking pan with olive oil. Transfer the chilled dough to the pan and gently stretch it to fit the corners. Cover and let rise at room temperature for 2 to 3 hours until noticeably puffy.
04 - Beat softened cream cheese, granulated sugar, egg yolk, vanilla extract, and lemon zest in a medium bowl until completely smooth and creamy. Set aside until ready to use.
05 - Toss fresh raspberries with 2 tablespoons granulated sugar and 1 tablespoon lemon juice in a small bowl. Let sit for 10 minutes to release some juices.
06 - Preheat oven to 425°F with oven rack in the center position.
07 - Dimple the risen dough thoroughly with oiled fingertips. Drop the cheesecake mixture in spoonfuls over the surface, then use a knife or spatula to gently swirl it into the dough. Scatter the sugared raspberries and their juices evenly across the top.
08 - Drizzle additional olive oil over the surface. Bake for 25 to 30 minutes until the top is golden brown, the center is set, and edges are crisp and pulling away from the pan.
09 - Let the focaccia cool in the pan for at least 30 minutes before slicing. Serve warm or at room temperature for best texture.