Preheat your oven to 200°C (390°F). Slice the tops off the bell peppers, carefully remove seeds and membranes, then brush the outside lightly with olive oil. Place them upright in a baking dish and set aside.
In a large skillet, warm the olive oil over medium heat until it shimmers. Add the diced onion and cook, stirring occasionally, until translucent and fragrant, about 5 minutes. Add the minced garlic and cook for another minute until it releases a savory aroma.
Stir in the cooked quinoa, rinsed black beans, smoked paprika, chili flakes, and a pinch of salt and pepper. Cook the mixture for 3-4 minutes, stirring often, until everything is heated through and fragrant. You should see the spices coating the grains and beans evenly.
Add the apple cider vinegar and chopped cilantro to the skillet, stirring to combine. Taste the filling and adjust the seasoning if needed. Remove from heat and let it cool slightly, about 2-3 minutes.
Using a spoon, carefully stuff each pepper with the filling, pressing gently to pack it in without spilling. Fill them to the top and ensure they’re well-seated in the dish.
Cover the baking dish with aluminum foil and bake for 25-30 minutes, until the peppers are tender and slightly blistered on top. The filling should be hot and bubbling when ready.
Uncover the peppers and, for extra smoky flavor and a bit of crunch, broil on high for 2-3 minutes until the tops are lightly charred. Keep a close eye to prevent burning.
Remove the peppers from the oven and let them rest for 5 minutes. Drizzle with a little more olive oil or a squeeze of lemon if desired, then serve warm, garnished with extra cilantro or herbs.
