In a large skillet or Dutch oven, cook the lean ground beef over medium-high heat until browned and fully cooked to an internal temperature of 160°F. Drain any rendered fat.
Add the onion and chopped bell peppers to the pan. Sauté for 5 minutes until the onion is translucent and peppers begin to soften.
Incorporate the minced garlic, tomato paste, oregano, and smoked paprika. Stir constantly for 60 seconds to toast the spices and paste.
Pour in the uncooked rice, diced tomatoes with their juices, and beef broth. Season with salt and pepper. Stir to ensure rice is submerged.
Bring the mixture to a boil, then immediately reduce heat to a low simmer. Cover with a tight-fitting lid and cook for 18 to 20 minutes until the rice is tender and the liquid is absorbed.
Remove from heat. Evenly distribute the shredded mozzarella cheese over the surface. Replace the lid and let sit for 2 minutes until the cheese is fully melted. Serve immediately.