Preheat the oven to 350°F (175°C).
In a large skillet, heat the olive oil over medium heat. Add the chopped onion and minced garlic, sautéing for 2-3 minutes until fragrant and softened.
Add the ground beef to the skillet, breaking it up with a spoon. Cook until browned and fully cooked through, about 5-7 minutes. Drain any excess fat.
Stir in the tomato sauce, water (or beef broth), Italian seasoning, salt, and pepper. Bring the mixture to a simmer for 5 minutes, allowing the flavors to combine.
Assemble the Casserole
In a 9x13-inch baking dish, spread the uncooked rice evenly on the bottom.
Pour the beef mixture over the rice, spreading it out evenly. Make sure the rice is covered with the sauce to ensure it cooks properly.
Top with Cheese
Sprinkle the shredded cheddar and mozzarella cheese evenly over the top of the casserole.
Bake the Casserole
Cover the baking dish with aluminum foil and bake for 30 minutes.
After 30 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.
Serve and Enjoy
Let the casserole rest for a few minutes before serving. Serve with a side of green beans or a simple salad for a complete meal.