To remove the zest from the lemon, grate the lemon on the small holes of a standard box grater, being sure not to include the bitter white layer just below the oily yellow citrus skin. Use a pastry brush to dislodge the zest that clings to the holes of the grater. Alternatively, use a citrus zester, which can be found in most kitchen specialty shops.

In a warmed serving bowl large enough to accommodate the pasta later, combine the lemon zest, lemon juice, olive oil, garlic cloves, olives, thyme, the 1 teaspoon of salt, and pepper to taste. Press on the garlic with the back of a wooden spoon to release its juices, and remove it just before you add the cooked pasta to the sauce.

To cook the pasta, bring the water to a rolling boil in a large pot. Add the pasta and the 2 tablespoons salt to it. Stir frequently to prevent the pasta from sticking together and continue to cook over high heat. Capellini will cook in approximately 3 minutes and spaghettini in about 5 minutes. Taste the pasta to determine its doneness; it should be al dente, that is, tender but quite firm to the bite. Do not overcook the pasta. If in doubt as to its doneness, drain it immediately, as the pasta continues to cook while it is hot. Take care not to overdrain; the pasta should be piping hot and still dripping when it is transferred to the serving bowl. Reserve some of the pasta cooking water.

Toss the hot pasta with the cold sauce. Capellini have a tendency, because of their fineness, to absorb moisture rapidly, and so it is often necessary to return some of the pasta cooking water to the sauce to prevent the capellini from clumping; the additional water will help to distribute the sauce easily through the strands. Serve piping hot.