Add a tablespoon of olive oil to the pan. Saute the onions and peppers, scrapping up any brown bits, until soft, about 5 minutes. Stir in the garlic, salt, and red chili. Cook another minutes, then carefully pour in the tomatoes. Simmer over medium heat, stirring occasionally, until the liquid has reduced and the tomatoes have softened, about 10 to 15 minutes. Stir in the pepperoncini and half the basil.