Preheat your oven to 200°C (390°F). Slice the tops off the peppers and carefully scoop out the seeds and membranes, creating a hollow cavity. Place the peppers cut-side up in a baking dish.
Roast the peppers in the oven for about 20 minutes until they’re slightly soft and their skins start to blister and char, which adds smoky depth. While they roast, prepare the filling.
Heat a large skillet over medium heat and add olive oil. Sauté the diced onion and minced garlic until fragrant and translucent, about 3 minutes. You’ll notice a sweet aroma filling the kitchen as the onions soften.
Add the cooked quinoa and mashed black beans to the skillet. Sprinkle in smoked paprika and cumin, stirring to coat everything evenly. Cook for another 2-3 minutes until the spices bloom and the mixture becomes fragrant.
Stir in the tomato paste and lemon juice, mixing thoroughly. The filling should turn a vibrant, slightly oozy consistency with a bright tang. Season with salt and pepper to taste.
Once the peppers are roasted and slightly cooled, carefully stuff each with the grain and bean filling, pressing gently to pack it in. Top with nutritional yeast if you like a cheesy flavor.
Return the stuffed peppers to the oven and bake uncovered for an additional 15 minutes, until the filling is bubbling and the tops are golden and slightly crispy. The blistered skins should be darkened and charred in spots.
Remove the peppers from the oven and let them rest for about 5 minutes. This helps the filling set and makes them easier to serve without spilling.
Gently transfer the peppers to serving plates, drizzle with extra lemon juice if desired, and enjoy while warm. The peppers should be tender with a smoky aroma, and the filling creamy and flavorful with a slight crisp on top.
