Preheat the oven to 375°F (190°C).
Cut the tops off the bell peppers and remove the seeds and membranes. Set aside.
In a medium saucepan, bring the vegetable broth to a boil. Add the quinoa, reduce heat to low, cover, and simmer for 15 minutes, or until the quinoa is cooked and the liquid is absorbed. Fluff with a fork.
In a large bowl, combine the cooked quinoa, black beans, corn, chopped onion, minced garlic, ground cumin, chili powder, smoked paprika, salt, and pepper. Mix well.
Stuff the bell peppers with the quinoa mixture and place them in a baking dish.
Cover the dish with foil and bake in the preheated oven for 20 minutes.
Remove the foil, sprinkle the tops of the peppers with shredded cheese (if using), and bake for an additional 10 minutes, or until the peppers are tender and the cheese is melted.
Garnish with fresh cilantro and serve immediately.
Enjoy your healthy and satisfying meal!