Preheat the oven to 375°F (190°C) and line a baking sheet with parchment paper. Wash the bell peppers, slice off the tops, and remove seeds and membranes. Arrange the hollowed peppers upright on the baking sheet.

In a medium saucepan, bring 2 cups of water to a boil. Rinse 1 cup of quinoa under cold water, add to boiling water, cover, and let simmer for about 15 minutes until fluffy. Fluff with a fork when done.

Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add 1 chopped onion and 2 minced garlic cloves; sauté for about 5 minutes until soft and fragrant.

In the skillet, stir in 1 can of drained black beans, 1 cup of corn, and 1 can of diced tomatoes. Season with 1 teaspoon each of cumin and chili powder, salt, and pepper to taste. Cook for 3-5 minutes until heated through.

In a large mixing bowl, combine the cooked quinoa with the vegetable mixture. Gently fold together until evenly mixed.

Spoon the filling into each hollowed bell pepper, packing it gently but firmly. Optionally, sprinkle shredded cheese on top.

Drizzle a little olive oil over the stuffed peppers, cover loosely with aluminum foil, and bake for 25 minutes.

Remove the foil and bake for an additional 10-15 minutes until peppers are tender and slightly charred. Cheese should be melted and bubbly if used.

Let the stuffed peppers cool for a few minutes. Garnish with freshly chopped cilantro or parsley if desired. Serve and enjoy!