Slice boneless roast beef across the grain, making thin strips of meat. Add the seasonings and chill. Before starting to cook the meat, cut 3 or 4 onions into quarters (smaller if large onions) and separate. Chunk up the green peppers. Quarter or cut some firm tomatoes into six sections, making wedges. Mix a little cornstarch with some beef broth and set aside.
Stir fry the onions with a little oil, keeping them on the move for a short time. Don't overcook, just cook until they start to lose their shape and become transparent. Add the green pepper and cook a short time then remove both vegetables from the pan. Add a little more oil, then stir fry the meat. It doesn't take long to cook, and then return the onions and peppers to the wok, combining with the meat. Add some beef broth, then the broth/corn starch mixture, a little at a time, to make a thin gravy. Watch and don't get it too thick. When the broth has boiled and thickened, taste. At this time, you can adjust seasonings, adding more soy sauce, curry, ginger, or garlic as desired. Do not add salt as the soy sauce provides salt. Just before serving, add in the tomato wedges and stir to coat. You don't want to cook the tomatoes, just stir them in and coat with the gravy. Take up to a platter and sprinkle with chopped green onions. Serve with rice.