In a large glass or stainless-steel bowl, toss the tomatoes with the garlic, oil, 1/2 teaspoon of the salt, the pepper, and basil. Set the mixture aside.
In a large pot of boiling, salted water, cook the fettuccine until just done, about 12 minutes.
Drain, return to the hot pan, and toss with the tomato mixture, the watercress, and the remaining 1/4 teaspoon salt.
Variations
Serve the pasta with a little bit of goat cheese crumbled over the top.
Wine Recommendation: With its fresh tomatoes and peppery watercress, this pasta requires a crisp, light red to bring out its best. See if you can find a ros-like grignolino from the Piedmont region of Italy. If not, a Valpolicella or Bardolino, both from the Veneto, will do nicely.