Sauté the chopped onion in olive oil until soft and translucent. Then add 500g (1 lb.) of cleaned and cut up squid (see Notes below). Allow the squid pieces to sauté along with the onion to absorb the flavors for a few minutes. (The squid will probably shed quite a bit of water, but that's perfectly normal. No need to try to boil if off.)

Add a splash of white wine, allow it to evaporate and then add the tomatoes. Mix everything well, lower the heat. Cover and simmer for 45 minutes to an hour, or until the squid is quite tender. (Add water if the sauce becomes too dense.)

Then add the peas (or more or less if you want—there is no real 'right' amount) and continue simmering until the peas are just cooked, about 5 minutes for frozen, 15-20 for fresh.

Adjust for seasoning and serve immediately.