Meanwhile, preheat oven to 450˚F. Sprinkle a rimless baking sheet with 1 tablespoon flour. On a lightly floured surface, roll out pizza dough to a 10-inch circle and transfer to prepared baking sheet. Prick dough all over with a fork. Spread dough evenly with ricotta cheese and sprinkle with salt. Top with sauteed onion mixture, red onion and mozzarella cheese.