1 cup Gaeta or Kalamata olives, pitted, or 1 Tbs. black olive paste (optional)
Red pepper flakes, to taste (optional)
If using cherry tomatoes, cut them in half through the stem end. If using larger tomatoes, cut them into pieces the size of a cherry tomato half. Put the cut tomatoes in a bowl and add the olive oil and one-third of the basil. Set aside at room temperature to allow the flavors to blend while you prepare the remaining ingredients.
Cut the mozzarella into 3/4-inch cubes or coarsely shred it with your hands. Set aside.
Bring a large pot three-fourths full of water (at least 4 quarts) to a rapid boil over high heat. Add the 1 Tbs. salt and the pasta and stir for the first minute of cooking and occasionally thereafter. Cook until al dente, according to the package instructions.
Just before the pasta is done, add the 1/2 tsp. salt and a few grinds of black pepper to the tomatoes. When the pasta is ready, drain it but not too dry and transfer to a serving bowl. Pour the tomato mixture over the pasta, add the anchovies, capers, olives and a sprinkle of red pepper flakes and stir well. Let the pasta cool for about 5 minutes, then stir in the mozzarella pieces. (The pasta should be cool enough so that the mozzarella does not melt.) Sprinkle with the remaining basil.
The pasta can be made up to 2 hours in advance and kept at room temperature; do not refrigerate. Spoon into individual bowls or onto plates, or serve in a large bowl as part of a buffet. Serves 4 to 6.
Adapted from Williams-Sonoma Foods of the World Series, Rome, by Maureen B. Fant (Oxmoor House, 2005).