Clean the squid, following the directions below. Cut the body crosswise into 1/2-inch rings. Cut the tentacles into 1-inch sections. Reserve the ink sacs.

Heat the olive oil in a nonstick skillet. Add the garlic, onion, and half the parsley and cook over medium heat until golden-brown, about 6 minutes. Add the tomatoes and cook until most of the juices have boiled away, about 3 minutes.

Stir in the squid and sauté for 1 minute. Add the wine, salt, and pepper and simmer until the squid are very tender, 20 to 30 minutes. Halfway through, squeeze the squid ink from sacs into the sauce. Correct the seasoning, adding salt and pepper to taste. Sprinkle the remaining parsley over the squid and serve at once.