Preheat your oven to 350°F (175°C).
In a large skillet, heat the olive oil over medium heat.
Add the chopped onion and minced garlic, cooking until the onion is translucent, about 3-4 minutes.
Add the ground beef to the skillet, breaking it up with a spatula. Cook until browned and fully cooked, about 5-7 minutes. Drain excess fat if necessary.
Stir in the diced tomatoes (with juice), tomato sauce, beef broth, cooked rice, oregano, chili powder, salt, and pepper. Mix well.
Transfer the mixture to a 9x13 inch baking dish, spreading it evenly.
Cover the dish with aluminum foil and bake in the preheated oven for 30 minutes.
Remove the foil and sprinkle the shredded cheddar cheese on top. Return to the oven and bake uncovered for an additional 15 minutes, or until the cheese is bubbly and golden.
Once done, let it cool for a few minutes before serving.