To make these Autumn Pumpkin Muffins gluten-free, use a certified gluten-free spice cake mix. Confirm that the pumpkin puree and any optional add-ins, such as chocolate chips, nuts, dried fruit, or cinnamon chips, are also certified gluten-free. If using cooking spray or muffin liners, verify that they are free from gluten-containing additives or cross-contamination concerns.