In a small bowl, mix together the harissa paste, olive oil, smoked paprika, garlic powder, ground cumin, lemon zest, and lemon juice to form a marinade.
Pat the chicken thighs dry with paper towels and place them in a large mixing bowl. Pour half of the marinade over the chicken, season with salt and pepper, and toss to coat evenly. Set aside to marinate for at least 15 minutes.
On a large sheet pan, spread the halved baby potatoes, sliced bell peppers, and onion wedges evenly. Drizzle with the remaining marinade and toss to coat the vegetables.
Push the vegetables to one side of the pan to create space for the chicken. Place the marinated chicken thighs skin side up on the other side of the pan.
Bake in the preheated oven for about 30-35 minutes, or until the chicken is cooked through (internal temperature should reach 165°F/75°C) and the skin is crispy. The vegetables should be tender and slightly charred.
Once cooked, remove the pan from the oven and let it rest for a few minutes.
Garnish the dish with fresh cilantro or parsley before serving.
Notes
Let the chicken marinate for more flavor if time allows.