In a medium stockpot, heat oil over medium heat. Add garlic, and cook until fragrant, about 30 seconds. Add tomatoes, salt, Italian seasoning, and red pepper, and bring to a low boil. Using a potato masher, mash tomatoes until only small chunks remain. Simmer, stirring occasionally and adjusting heat if needed, until thickened and no liquid is separated and sitting on top of sauce, about 45 minutes. Let cool completely before using. Cover and refrigerate for up to 5 days.