Italian "Polpo alla Luciana". Simply delicious.
My Recipe:
Defrost octopus, cut in pieces, place in large pot with a drizzle of olive oil, a bit of onion (sliced), some garlic, cut cherry tomatoes, some olives, some capers, a bit of chili (if you like). Seal the pot with glad wrap tied around the rim with a string (needs the be really sealed). Let it cook in it's own liquid for two hours on very low.
Take the glad wrap away, let it cook until the liquid has thickened a bit. Let rest for 5-10 min...