In a 4-quart saucepan, bring 3 quarts of water to a boil over high heat.
Add pasta, and cook according to package directions for the shortest recommended time, about 10 minutes. Drain.
Meanwhile, in a large nonstick pan, heat olive oil over medium heat. Add onion. Cook and stir for 5 minutes, until onion begins to soften.
Add garlic, cayenne pepper, and anchovy paste. Cook and stir another 5 minutes.
Add chopped tomatoes, capers, and olives. Cook and stir until heated through.
6
Divide pasta among four dinner plates (about 1½ cups each). Spoon sauce over pasta. Garnish with parsley if desired.