Steps
1. Preheat the oven to 375°F (190°C).
2. Cut the top off the bell pepper and remove the seeds and membranes.
3. In a bowl, combine the cooked quinoa, black beans, onion, garlic, cumin, salt, and pepper.
4. Stuff the mixture into the bell pepper, packing it gently.
5. If using cheese, sprinkle it on top of the stuffed pepper.
6. Place the stuffed pepper in a small baking dish and cover it with foil.
7. Bake for 25-30 minutes, until the pepper is tender.
8. Remove from the oven, garnish with cilantro, and serve warm.