Start by cleaning the octopus under cold running water, and removing the head and beak if necessary. Tenderize the octopus by pounding it gently or freezing it and thawing overnight.
In a large pot, bring water to a boil. Add the octopus and reduce the heat to low. Simmer gently for 1 to 1 ½ hours, or until the octopus is tender when pierced with a fork.
Once cooked, remove the octopus from the pot and let it cool. Optionally, you can then slice the octopus into smaller, more manageable pieces.
Preheat a grill or skillet over medium-high heat. Drizzle the octopus with olive oil and season with salt, pepper, and any desired herbs or spices.
Grill or sear the octopus for about 3-4 minutes per side, until it develops a golden brown colour and is heated through. Alternatively, you can roast it in the oven at 425°F (220°C) for 15-20 minutes.
Remove from heat and let the octopus rest for a few minutes before serving.
Serve the octopus as a standalone dish or as part of a larger seafood feast. Pair it with fresh lemon wedges, a drizzle of olive oil, and your favourite sides.