Trim fat from steak. Score steak on both sides. Place steak in a heavy-duty, zip-top plastic bag.
Coat a small nonstick skillet with cooking spray; place over medium-high heat until hot. Add onion and garlic; saute until tender. Add beef broth and remaining ingredients, and bring to a boil; boil 1 minute. Let cool. Pour marinade over steak; seal bag, and shake until steak is well coated. Marinate steak in refrigerator 8 hours, turning bag occasionally.
Remove steak from bag, and discard marinade. Place steak on rack of a broiler pan coated with cooking spray. Broil 5 1/2 inches from heat (with electric oven door partially opened) 6 to 7 minutes on each side or to desired degree of doneness. Let stand 10 minutes. Cut steak diagonally across grain into 1/4-inch-thick slices.