In a large pot or Dutch oven, melt the butter over medium heat. Add the sliced sausage and cook until browned, about 5-7 minutes.
Add the diced onion and minced garlic to the pot. Sauté for another 3-4 minutes until the onion is translucent.
Stir in the orzo pasta, chicken broth, Italian seasoning, salt, and pepper. Bring to a boil, then reduce the heat to low. Cover and simmer for about 10-12 minutes, or until the orzo is tender and most of the liquid is absorbed.
Add the cherry tomatoes and fresh spinach to the pot. Stir until the spinach wilts, about 2-3 minutes.
Remove from heat and stir in the grated Parmesan cheese. Adjust seasoning if necessary.
Serve warm, garnished with fresh parsley.