In a large bowl, whisk active sourdough starter and warm water. Add bread flour and stir into a shaggy dough. Cover and rest (autolyse) for 30 minutes.

Add sea salt and olive oil. Perform 3 sets of stretch-and-folds every 30 minutes. Let dough bulk ferment at warm room temp for 4 to 6 hours until doubled.

Divide dough into 2 equal balls. Shape into tight rounds, cover, and let rest for 1 hour (or refrigerate up to 72 hours).

Preheat oven with a pizza stone on top rack to 500-550°F (260-290°C) for 45 minutes.

Dust peel with semolina, stretch dough by hand into a 12-inch round leaving a puffy rim. Top with crushed tomatoes and mozzarella. Bake on stone for 7-9 minutes until blistered and charred!