Combine the pineapple juice, vinegar, molasses, salt and several grinds of black pepper. Add the cubes of beef and allow to stand in the marinade at room temperature for 1 hour. Drain, reserve marinade to use as a basting sauce.
Meanwhile drop the onions into boiling water and simmer for 8 minutes. Drain, and when cool slip off the skins.
Thread the meat, onions, tomatoes, green