Cook the quinoa: Rinse quinoa under cold water. Cook according to package directions (typically 1 cup quinoa to 2 cups water, simmer 15 minutes). Fluff with a fork and set aside.

Preheat oven: Set oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish with cooking spray or olive oil.

Prepare the peppers: Cut bell peppers in half lengthwise, leaving stems intact if desired. Remove all seeds and white membranes. Arrange cut-side up in the prepared baking dish.​

Make the filling: Heat 2 tablespoons olive oil in a large skillet over medium heat. Add diced onion and sauté for 4-5 minutes until softened and translucent. Add minced garlic and cook for 30 seconds until fragrant.​

Add vegetables and spices: Stir in corn, black beans, diced tomatoes, chili powder, cumin, smoked paprika, salt, and pepper. Cook for 5 minutes, stirring occasionally, until heated through.

Combine with quinoa: Remove skillet from heat. Stir in the cooked quinoa, fresh cilantro, and lime juice. Mix well to combine. Taste and adjust seasonings as needed.

Stuff the peppers: Generously fill each pepper half with the quinoa mixture, pressing down gently to pack it in. Drizzle tops lightly with olive oil.

Bake covered: Cover the baking dish tightly with aluminum foil. Bake for 30 minutes until peppers are tender.

Add cheese and finish: Remove foil, sprinkle shredded cheese over each pepper (if using), and bake uncovered for an additional 5-8 minutes until cheese is melted and bubbly. For extra browning, broil for 1-2 minutes.

Serve: Let cool for 5 minutes before serving. Garnish with fresh cilantro, avocado slices, a dollop of Greek yogurt, and lime wedges.