In a large skillet, heat olive oil over medium heat. Add chopped onion and garlic, sauté until onions are translucent.
Add ground beef to the skillet. Cook until browned, breaking it up with a spoon as it cooks.
Stir in the rice, cream of mushroom soup, diced tomatoes, salt, and pepper. Mix well and transfer to a casserole dish.
Cover the casserole dish with foil and bake for 30 minutes. Remove foil, sprinkle with cheese, and bake for an additional 10-15 minutes or until cheese is melted and bubbly.
Notes
Let the casserole rest for 5 minutes before serving. Garnish with fresh parsley, if desired.