Preheat your oven to 200°C (390°F) and prepare a baking dish.
Slice the tops off the peppers and carefully scoop out the seeds and membranes, creating hollow boats. Place them upright in the baking dish.
Rinse the quinoa thoroughly, then combine it with water in a pot. Bring to a boil, reduce heat, cover, and simmer for about 15 minutes until fluffy. Fluff with a fork and set aside.
Heat a tablespoon of oil in a skillet over medium heat. Add the diced onion and sauté until fragrant and translucent, about 3-4 minutes. Add the minced garlic and cook for another minute until aromatic.
Stir in the cooked quinoa, black beans, corn, and smoked paprika. Mix well to combine, allowing the flavors to meld for a minute or two. Season with salt and pepper, then squeeze in fresh lemon juice for brightness.
Carefully spoon the filling into each hollowed-out pepper, pressing gently to pack in the mixture. Place the stuffed peppers upright in the baking dish.
Bake in the preheated oven for 20-25 minutes, until the peppers are blistered and slightly charred, and the filling is bubbling and heated through.
Remove the peppers from the oven and let them rest for 5 minutes. Garnish with chopped fresh cilantro or parsley for a burst of color and freshness.
Serve warm, enjoying the smoky aroma and vibrant colors. The peppers should be tender yet hold their shape, with a slightly crispy top.