Place your baby octopus, whole, into a pot (traditionally terracotta but enameled cast iron or even a heavy stainless or copper pot will do fine) together with about half as much by weight of canned tomatoes, a drizzle of olive oil, some chopped garlic, a dash of salt and, if you want a little heat, some red pepper flakes.
Cover tightly and simmer over lowish heat for 45 minutes to an hour. By this time, the octopus should be tender and the sauce should be nice and thick, and rather darker than when it started. If the octopus is done but the sauce still rather thin, which can happened since octopus tend to shed liquid while cooking, you can fish them out of the sauce and continue reducing until you have the right consistency, then add the octopus back in to heat up again. If, on the other hand, the sauce has reduced but the octopus still needs some more cooking, then just add a bit of water and continue simmering. About 5-10 minutes before the dish is done, add some chopped parsley.
Serve your Braised Baby Octopus hot, with a bit of the sauce and, if you like, some more parsley and/or a drizzle of olive oil on top.