1. Preheat the oven to 350°F (175°C).
2. Cook the rice according to the package instructions and set aside.
3. In a skillet, cook the chicken tenderloin with onions until tender and fully cooked. Season with your preferred spices.
4. In a large mixing bowl, combine the cooked chicken, rice, cream of mushroom soup, and half of the mozzarella cheese.
5. Transfer the mixture to a greased casserole dish and spread evenly.
6. Top with the remaining mozzarella cheese.
7. Bake in the preheated oven for 20-30 minutes or until the cheese is golden and bubbly.