To make this Chicago Spaghetti gluten free, substitute the thick spaghetti with a certified gluten-free spaghetti or another gluten-free pasta shape that holds sauce well. Check the labels on the Italian sausage, tomato paste, crushed tomato, Parmesan cheese, and dried seasonings to confirm they are gluten free and free from cross-contact risks. The rest of the ingredients are typically naturally gluten free, but label-checking is especially important when preparing the dish for someone with celiac disease or gluten sensitivity.