Step 1: Preheat your oven to 400°F (200°C). Toss the cubed sweet potatoes with olive oil, salt, and pepper on a baking sheet. Roast for 20-25 minutes until tender.
Step 2: While the potatoes roast, combine quinoa and water/broth in a saucepan. Bring to a boil, then reduce heat, cover, and simmer for 15 minutes until liquid is absorbed. Fluff with a fork.
Step 3: In a large bowl, mix the roasted sweet potatoes, cooked quinoa, black beans, cumin, paprika, and chili powder. Adjust seasoning with salt and pepper.
Step 4: Slice the tops off the bell peppers and remove the ribs and seeds. Stand them upright in a baking dish.
Step 5: Generously fill each pepper with the sweet potato and quinoa mixture, pressing down gently to pack it in.
Step 6: Add a splash of water to the bottom of the baking dish and cover tightly with foil. Bake for 30 minutes.
Step 7: Remove the foil and bake for an additional 10-15 minutes until the peppers are soft and the tops are slightly golden.
Step 8: Garnish with fresh cilantro and serve warm with lime wedges.