01 - Heat oven to 425°F. Line a large baking sheet with parchment paper.
02 - In a large bowl, combine harissa paste, olive oil, smoked paprika, ground cumin, salt, pepper, and minced garlic. Mix thoroughly.
03 - Add chicken thighs to the marinade and toss until fully coated. Allow to marinate for at least 10 minutes, or refrigerate up to 2 hours for enhanced flavor.
04 - Place sweet potato cubes and red onion wedges on the prepared baking sheet. Drizzle lightly with olive oil, season with salt and pepper, and toss to coat evenly.
05 - Set the marinated chicken thighs atop the sweet potatoes and onions in a single layer.
06 - Bake in the preheated oven for 40 to 45 minutes, until chicken reaches an internal temperature of 165°F and sweet potatoes are tender and caramelized.
07 - Transfer to serving plates, sprinkle with chopped cilantro or parsley, and accompany with lemon wedges.