Clean the squid by pulling the head out of the pouch and with it the soft innards and transparent spine . Peel off the reddish membrane from the body and rinse out the mucous membrane from inside
Remove the eyes from the rest of the head and discard. Cut the body into rings 1 cm thick and the tentacles into small pieces.
Heat the oil in a pan and fry the onion until soft and golden. Add the garlic and fry until it begins to colour, then add the tomatoes, vinegar and saffron, if used. Season with salt and pepper.
Put the squid in the sauce, adding just enough water to cover. Simmer for 4-5 minutes for baby squid or until the squid is tender and opaque – this can take as long as 45 minutes for large squid. You must watch the squid constantly, as the flesh hardens quickly if overcooked.
Add the herbs and serve with bread or on a bed of rice.