Heat your grill to medium heat. If you're not using a grill, heat a griddle pan or skillet over medium heat.
Lightly oil the octopus tentacles. Cook on the grill for 2 minutes, then flip and cook for another 2 minutes until lightly charred. If cooking indoors, cook for the same amount of time on your griddle pan or skillet.
Remove and slice into 1-2 inch pieces.
Serve in tortillas, top with diced white onion, avocado, radish and red cabbage. Serve with lime wedges and cilantro.