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, mix the cooked quinoa, black beans, diced tomatoes, cumin, chili powder, salt, and pepper until well combined.
4. Stuff the bell pepper with the quinoa mixture, pressing down gently to pack it in.
5. Place the stuffed pepper upright in a baking dish and sprinkle with cheese, if using.
6. Bake for 25-30 minutes, or until the pepper is tender.
7. Remove from the oven, garnish with fresh cilantro, and serve warm.