In a medium size pot filled with water, add octopus, coarsley chopped carrots, quartered onion, chopped celery and one whole lemon cut in half.
Bring pot to a boil, then lower heat to a simmer and cook for a total of 40 minutes.
Remove octopus from the liquid and discard rest of contents from pot.
Chop the octopus into small pieces but be careful not to chop the octopus too finely.
In a bowl, whisk the juice from a whole lemon into a quarter cup of extra virgin olive oil until dressing becomes emulsified. Add salt and pepper to taste then stir in the chopped parsley.
Line a plate with lettuce and place your desired portion of octopus on top of the lettuce.
Drizzle the lemon vinegarette over the octopus.
You can also add chopped tomatoes to this salad or you can serve this salad into a hollowed out tomato.