Place the meat strips into the small bowl. Stir together the marinade ingredients and pour over the beef, stirring until all of the beef is coated. Put in the refrigerator and allow to marinate at least 30 minutes or as long as 3 hours.
In the medium pot, steam or parboil the broccoli florets just until the color changes to a bright green. Drain and rinse with cold water, then set aside.
Preheat the wok over high heat, then add 2 tablespoons of the canola oil and the broccoli. Stir-fry for about 5 minutes, until the broccoli is crisp-tender. Remove broccoli from the wok and set aside.
Add up to 2 more tablespoons of canola oil and the garlic. Stir for a just 30 seconds, then add the beef slices. Stir-fry for 3 to 4 minutes, until the meat is just a little short of done. Add the broccoli back to the wok.
Pour the oyster sauce, soy sauce, and chicken broth into the wok and stir. Make a well in the middle. Stir together the cornstarch and cold water and pour into the center of the wok, stirring to incorporate. The sauce should start to thicken almost immediately. Lay the tomatoes on top of the stir-fry and turn off the heat, allowing the dish to sit for just a minute or two. Serve with hot rice.