This Greek-style vinegar-marinated octopus is slow-cooked until tender and finished with a bright dressing of olive oil, vinegar, herbs, and capers for a flavorful Mediterranean seafood dish.
Heat a deep pot over medium heat and drizzle in a little olive oil. Add the onion, fennel, celery, carrot, Florina pepper, bay leaves, and peppercorns.
Separate the tentacles from the head of the octopus and place the octopus on top of the vegetables.
Reduce the heat to medium-low, cover the pot with a lid, and let the octopus cook slowly in its own juices for about 1 hour, until tender.
After about an hour, check the octopus with a knife to see if it is tender. Remove from the heat and allow it to cool completely.
Once cooled, slice the octopus into pieces and transfer it to a bowl.
In a separate bowl, mix all the marinade ingredients. Pour the marinade over the octopus, toss gently, and serve.