In a medium pot, combine the rinsed quinoa and vegetable broth. Bring to a boil over medium-high heat.

Once boiling, reduce the heat to low, cover, and simmer for about 15 minutes or until the quinoa is fluffy and the liquid is absorbed. Remove from heat and let it sit covered for 5 minutes.

In a large mixing bowl, combine the cooked quinoa, black beans, corn, cumin, chili powder, garlic powder, onion powder, and diced tomatoes. Mix well to combine all ingredients evenly.

Taste the mixture and adjust seasoning if necessary. You can add salt and pepper to taste.

Preheat your oven to 375°F (190°C).

While the oven is preheating, prepare the bell peppers. Cut the tops off and remove the seeds and membranes. Rinse them under cold water.

Place the bell peppers upright in a baking dish. Spoon the quinoa filling into each pepper, packing it down gently to ensure they are well filled.

If using, sprinkle shredded cheese on top of each stuffed pepper.

Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes.

After 25 minutes, remove the foil and bake for an additional 5-10 minutes, or until the peppers are tender and the cheese is melted and bubbly.

Remove the stuffed peppers from the oven and let them cool for a few minutes before serving.

Garnish with sliced avocado and chopped cilantro if desired. Enjoy your healthy stuffed bell peppers!