Lemon-Sage Vinaigrette: Place lemon juice, shallot, garlic and honey in a medium saucepan and reduce to 1/2 cup. Place reduced syrup into a blender, add olive oil, salt and pepper and blend until smooth. Pour into a bowl and fold into the sage.
Sweet Onion Salad: Heat olive oil in a large saute pan with sugar over medium heat. Add the onions and cook until soft and caramelized. Add the vinegar and cook until reduced. Season with salt and pepper.
Octopus: Place the octopus, water, vinegar, corks, garlic, bay leaf and peppercorns in a medium saucepan and bring to a simmer over medium heat and cook until tender, about 1 1/2 hrs. Remove the octopus from the water and place on a platter lined with paper towels. Heat the grill or grill pan. Cut the octopus into pieces, brush with olive oil, season with salt and pepper and grill for 1 to 2 minutes on each side.
Assembly: Place the octopus on a platter, drizzle with the vinaigrette, top with the onion slices and sprinkle with the fresh herbs.