Prep the Oven and Peppers: Preheat the oven to 350 F (180 C). Cut each bell pepper in half horizontally and remove the seeds and ribs. Place the halved bell peppers in a baking dish, cut sides up, and add 1/2 cup of water. Partially bake them in the preheated oven for 15 minutes to soften them a bit. Remove to a rack and set aside.

Prepare the Chorizo Filling:  Heat the oil in a skillet over medium-high heat; add the chorizo and cook for 4 minutes. Add the onion and garlic to the chorizo and continue to cook for 4 to 6 minutes or until the chorizo is no longer pink and the onions are translucent. Add the tomato paste, chili powder, cumin, salt, pepper, and red pepper flakes to the skillet and stir until combined. Stir in the cooked rice and 1/2 cup of the mozzarella cheese. Taste and adjust the seasonings as needed. If the mixture seems very dry, add a few tablespoons of water or broth to moisten.

Stuff the Peppers: Fill the peppers with the chorizo and rice mixture.

Bake: Bake the stuffed peppers for 20 minutes, then top each pepper with mozzarella cheese. Return the peppers to the oven and continue baking for 4 to 6 minutes or until the cheese is melted. Alternatively, broil them for a few minutes to brown the cheese a bit.

Serve: Serve stuffed peppers with a garnish of chopped cilantro or parsley. Enjoy!