With a sharp knife, trim fat from beef. Cut beef across grain into ⅛ inch thick strips.

Combine soy sauce, garlic and ginger in a bowl and set aside.

Add beef strips into soy sauce mixture and toss together.

Heat oil in a large frying pan or a wok. Once heated, add beef and toss over high heat until the meat is browned. Cover and simmer for 30-40 minutes over low heat.

Prepare vegetables and then add to beef mixture once beef is tender, which will be about 30-40 minutes. Turn up heat to medium/high and toss until vegetables are tender but crisp, about 10-15 minutes.

Mix cornstarch and water together in a separate bowl and then add to pan. Stir and cook until liquid has thickened up.

Add tomatoes and heat.