In a boiling pot of water, aprox 5 cups, add in the onion, rosemary and salt/pepper. Let boil for 5 minutes
Remove pot from heat and add in the octopus and let stand for 1 minute
Immediately remove octopus from water and chill quickly in an ice bath, about 2 minutes
For Marinade – combine the olive oil, lemon juice, salt/pepper and herbs together.
Combine the marinade and octopus together and let refrigerate for 2-4 hours.
Preheat grill to high heat
Skewer octopus and cook on high heat, letting the flames char the outside