Preheat your oven to 375°F (190°C).
Cut the tops off the bell peppers and remove the seeds and membranes. Place them upright in a baking dish.
In a medium pot, combine the rinsed quinoa and vegetable broth. Bring to a boil, then reduce heat and simmer for about 15 minutes, or until the quinoa is fluffy and the liquid is absorbed. Remove from heat and let it cool slightly.
In a skillet over medium heat, combine the black beans, corn, diced tomatoes, cumin, chili powder, garlic powder, salt, and pepper. Stir and cook for about 5-7 minutes until heated through.
In a mixing bowl, combine the cooked quinoa with the bean mixture. Stir to combine well.
Spoon the quinoa mixture into each prepared bell pepper, packing it down gently.
Top each stuffed pepper with shredded cheese.
Cover the baking dish with aluminum foil (optional) and bake in the preheated oven for 25 minutes. Remove the foil and bake for an additional 10 minutes, or until the peppers are tender and the cheese is melted and bubbly.
Remove from the oven and let cool for a few minutes. Garnish with fresh cilantro if desired.
Serve warm and enjoy!