Combine flour and salt in a large bowl. Mix in 1 ½ cups water and sourdough starter to make a stiff dough. Cover with plastic and set in a draft free place for 12-18 hours until doubled.
Spread a small amount of flour on a clean counter and dump out dough on top. Press into a large rectangle, fold over on itself and repeat a few times. Spread into a large rectangle
Grease a jelly roll pan (or baking sheet with sides) 2 tablespoons olive oil.
Place the dough into the greased pan, press and stretch it to fit the pan, making dimples in the dough as you stretch it. Coat the top with 1 to 2 tablespoons olive oil.
Cover the pan and let rise in a warm place until doubled, 45 minutes to 1 hour.
Preheat oven to 425 ℉ . Top the dough with Parmesan, rosemary and tomatoes.