Preheat oven to 425°F. Oil a large roasting pan and set aside. In a small bowl, combine paprika, cumin, sea salt, pepper, garlic, vinegar and oil to make a paste. Place onions in a large bowl and toss with 2 tablespoons of the paste.
Rub chicken pieces with remaining paste and place in prepared pan, then cover with onions, peppers and lemon. Roast, basting occasionally with pan juices, until chicken is cooked through and vegetables are very tender, about 45 minutes.
Remove from oven and let rest 5 minutes before serving.