preheat oven to 400 degrees and grease a 9×14 casserole dish.
Add onion, garlic, bell pepper, mushrooms, and spices to the base of the dish, followed by uncooked pasta, melted ghee, marinara sauce, and milk. Give it a good stir until everything is combined. Cover with foil, and bake for 35-40 minutes.
Remove foil, fold in spinach and top with grated parmesan. Increase temp to 475 and bake another 5-6 minutes or so, until spinach is cooked and cheese is golden and bubbling.