To make this Sunday Sauce gluten-free, replace the Italian-seasoned breadcrumbs in the meatballs with a certified gluten-free breadcrumb blend. Also, ensure the Parmesan cheese and Italian sausage used are labeled gluten-free, as some commercial products may contain additives or fillers with gluten. Confirm the tomato products are pure and without added thickeners. When serving, pair the sauce with gluten-free pasta or polenta.