Sauté the Vegetables: Heat olive oil in a large skillet over medium heat. Add diced onions and bell peppers, cooking until softened (about 3-4 minutes). Stir in the minced garlic and cook for another 30 seconds.
Brown the Beef: Add the ground beef, breaking it apart with a spoon. Cook until browned and no longer pink. Stir in oregano, chili powder, cumin, paprika, salt, black pepper, and red pepper flakes (if using).
Cook the Rice: Mix in the tomato paste, uncooked rice, beef broth, and fire-roasted diced tomatoes (with juices). Stir to combine, then bring to a boil. Reduce heat to low, cover, and let simmer for 20-25 minutes, stirring occasionally, until the rice is tender.
Melt the Cheese & Serve: Remove from heat, sprinkle shredded cheddar cheese on top, and cover for 2-3 minutes until the cheese melts. Serve warm and enjoy!