Preheat your oven to 190°C (375°F). Lightly oil your baking dish and set aside.
Cut the tops off each bell pepper and scoop out the seeds and membranes, creating a hollow cavity. Bring a large pot of water to a boil, then blanch the peppers for about 5 minutes until slightly softened. Carefully remove and drain them, setting aside.
While the peppers blanch, rinse the quinoa under cold water and cook according to package instructions, until fluffy and water is absorbed. Fluff with a fork and set aside.
In a large mixing bowl, combine the cooked quinoa, finely chopped onion, minced garlic, diced tomatoes, smoked paprika, cumin, and olive oil. Season with salt and pepper to taste. Mix thoroughly until well incorporated.
Gently stuff each softened pepper with the filling, pressing down lightly to pack it in. Stand the peppers upright in the prepared baking dish.
Cover the dish with aluminum foil to trap steam and bake for about 20 minutes, until the peppers are tender and the filling is heated through.
Remove the foil and sprinkle the nutritional yeast over each pepper to add a cheesy, savory note. Return to the oven and bake uncovered for an additional 5-10 minutes, until the tops are bubbling and slightly browned.
Once baked, carefully remove from the oven and let rest for 5 minutes. Garnish with chopped cilantro or parsley for a fresh finish.
Serve the stuffed peppers warm, perhaps with a side salad or crusty bread for a complete meal. Enjoy the fragrant, smoky, and savory flavors!