To make this recipe gluten free, replace the whole-wheat flour with a certified gluten-free all-purpose flour blend or another gluten-free flour that works well for binding. Also confirm that any frozen spinach nuggets and shredded cheese used are labeled gluten free, as ingredients and processing methods may vary by brand. The remainder of the ingredients are typically naturally gluten free, but it is always best to verify packaging if cooking for someone with celiac disease or gluten sensitivity.