To make Trisha Yearwood’s Spinach Casserole gluten free, replace the breadcrumbs with certified gluten-free breadcrumbs or crushed gluten-free crackers. Verify that the frozen spinach, Parmesan cheese, cream cheese, heavy cream, butter, nutmeg, cayenne pepper, salt, and black pepper are labeled gluten free or free from gluten-containing additives. Use clean cookware, utensils, and a clean baking dish to prevent cross-contact with gluten-containing foods.