Fill a large pot with water; add the octopuses, white onion halves and bay leaf. Bring to a boil, then reduce the heat to medium. Simmer until the octopuses are very tender, about 2 hours. Drain, discarding the onion and bay leaf. Let the octopuses cool; cut into small pieces.
Melt the butter in a large nonstick skillet over medium-high heat. Add the red onion and cook, stirring, until fragrant, about 6 minutes. Add the garlic and chiles and cook, stirring, until tender, 3 more minutes. Add the octopuses and saute until lightly browned, about 5 minutes. Season with salt and pepper. Serve in tortillas; top with cilantro and diced white onion. Serve with lime wedges.