Chinese beef and tomatoes

4 md Tomatoes
      2 lb flank steak
      3 tb soy sauce
      2 tb Dry sherry
      1 cl garlic,minced
    1/2 ts Ground ginger
    1/8 ts Ground black pepper
      2 tb Oil
      1 md Green pepper,sliced
      1 md Onion,sliced
      1    Beef bouillon cube
    3/4 c  Boiling water
      2 tb Cornstarch
      2 tb Cold water
 
   Thinly slice beef on the diagonal (for easy slicing,place meat in the
  freezer until slightly frozen);place in  a  snug-fitting bowl.Combine soy
  sauce,sherry,garlic,and black pepper;pour over meat,tossing to coat
  completely.Cover and refrigerate 8 to 10 hours.
   In a large skillet or wok,heat oil. Add green pepper and onion saute for 2
  minutes.Dissolve bouillon cube in boiling water. Add beef and
  marinate.Bring to boiling point.Reduce heat and simmer,covered for 8
  minutes.Blend cornstarch with cold water. Stir into mixture in skillet.Cook
  and stir until thickened.Cut tomatoes into wedges;add to skillet;stir
  gently.Cover and simmer, just until tomatoes are hot,about 3 minutes.Serve
  hot over rice with scallions,if desired.Serves 6 to 8.