1. In a bowl mix the chili powder, cumin, tomato paste, garlic and lime juice. Rub the paste over the chicken. Cover and chill at least 4 hours.
2. Place each chicken quarter and a slice of onion on a square of foil. Fold into a package and seal the edges. Bake in a moderate oven (350ยบ) for 1 1/2-2 hours. Serve the chicken in the foil.