In a large bowl, combine the cornstarch, soy sauce, 2 tablespoons water and 1 tablespoon oil until smooth; add beef and toss to coat.
In a large skillet or wok, stir-fry beef, garlic and ginger in remaining oil until meat reaches desired doneness. Remove meat with a slotted spoon and keep warm. Add the onion, celery, green pepper and remaining water to the skillet. Cover and cook for 2 minutes. Add tomatoes and beef.
For sauce, combine the cornstarch, water, ketchup, soy sauce and curry until smooth; add to the skillet. Bring to a boil; cook and stir for 2 minutes. Serve with rice.