Prep ingredients: Melt butter in a microwave safe dish. Finely chop onion. Chop macadamia nuts. Chop rosemary.
Heat a large skillet over medium heat. Add a tablespoon of melted butter and chopped onions and saute for 1 minute to soften. Next, add the chopped macadamia nuts to the skillet and toast, constantly stirring, for 2 minutes.
Remove the skillet from heat and stir in the stuffing mix, tart cherries, and herbs.
Add the broth and stir well to combine the gluten-free bread stuffing mixture. Taste and add salt, pepper, and additional herbs if needed.
Spread the stuffing mixture in a single layer in the cast iron pan. Cover with aluminum foil and bake at 350 F for 20-25 minutes. If you like your stuffing crispy on top, remove the foil after 15 minutes and bake an additional 5-10 minutes or until golden brown. Note: If you don't have an oven-safe skillet, add the stuffing to a prepared baking dish with cooking spray and bake per the above instructions.
Serve immediately. Or, go ahead and store it in an airtight container in the refrigerator for up to three days. Note: You may need to add additional vegetable broth before reheating if you prefer a moister stuffing.