In large nonstick skillet, combine asparagus and 1/4 cup water; bring liquid to a boil. Reduce heat to low; simmer 2 min., until asparagus is just tender and water is evaporated. Sprinkle beef on all sides with salt and pepper; add beef, scallions and garlic to cooked aspsragus. Cook, stirring frequently, 4 min., until beef is cooked through. Add tomatoes; cook, stirring frequently, 2 minutes, until tomatoes are just heated through.