Prepare marinade: mix olive oil, grated onions, saffron, salt and black pepper. Wash and cut chicken into small pieces, then remove the skin. Marinate overnight (or at least for several hours) in refrigerator. The container should be covered.
Thread chicken on long, thin metal skewers. Thread leg and thigh pieces, wings and breast pieces separately, as breast requires slightly less cooking. Also thread whole tomatoes separately on another skewer. Brush with marinade. Barbeque for about 5-10 minutes on each side, turning frequently. Joojeh Kabab can also be prepared in the oven. Prepare chicken as before, pre-heat the grill to a high temperature, and place just under the grill, again turning frequently. Serve hot with basmati rice or on middle-eastern bread.