Pizza dough (recipe above) or your favorite, prepared as directed.
5 to 7 tablespoons olive oil, divided
1 medium onion, chopped
3 cloves garlic, minced
4 cup diced fresh tomatoes
1/4 teaspoon sugar, or to taste salt and freshly ground pepper, to taste
1/4 cup loosely packed fresh basil leaves, cut in thin strips
3/4 to 1 pound fresh mozzarella cheese, sliced 1/8-inch thick