1. To make marinade combine lime juice, fish sauce, sugar, and garlic clove in a 9-inch glass pie plate; add beef and let stand 10 minutes.
2. Meanwhile, make dressing by combining lime juice, fish sauce, lite soy sauce, sugar, sesame oil, fresh ginger, garlic clove, jalapeno, and pineapple juice in a cup. Set aside.
3. In a large bowl toss the watercress, onion, and basil. Set aside.
4. Remove beef from marinade and pat dry with paper towels. Heat 1-1/2 teaspoons oil in a large nonstick skillet over high heat. Add half the beef and cook 1-1/2 to 2 minutes until well browned. Transfer to a plate. Repeat with remaining oil and beef. Let cool 5 minutes.
5. Toss the watercress mixture and pineapple with the dressing, then top with beef. Serve immediately. Makes 4 servings.