To make this grilled chicken tikka masala recipe gluten-free, ensure that the plain yogurt, spices, tomato sauce, and heavy cream are all labeled gluten-free, as some brands may contain thickeners or additives with gluten. Also, verify that your skewers and grill tools are free of cross-contamination. Serve with gluten-free naan or basmati rice for a completely gluten-free meal.