Grill, covered, over medium heat or broil 4 in. from the heat for 6-9 minutes on each side or until meat reaches desired doneness (for medium-rare, a thermometer should read 135°; medium, 140°; medium-well, 145°).
Meanwhile, in a large skillet, saute onion and mushrooms in butter until tender. Stir in the tomatoes, water, basil, bouillon and pepper. Bring to a boil; cook and stir over medium heat for 5 minutes or until thickened. Serve with beef.