1. Cook pasta according to package directions.
2. Place the cheese in a large bowl; top with the watercress. Before draining the pasta, take 1/4 cup of the cooking water from the pot and pour it over the watercress. (Watercress will wilt slightly and cheese will get soft.)
3. Place the tomatoes in a colander. Drain the pasta over the tomatoes for a super-quick blanch.
4. Toss with the watercress and cheese; sprinkle with pepper and serve.