My mom’s famous recipe for Octopus Casserole with Potatoes:

Ingredients

Octopus: 2 lbs, cleaned and cubed
Aromatics: 1/4 cup olive oil, 2 red onions, 4 cloves garlic
Base: 1 cup red wine, 14 oz crushed tomatoes, 1 tbsp tomato paste
Starch & Seasoning: 2 large potatoes (cubed), bay leaves, allspice, cinnamon stick, salt, pepper

Instructions

Sauté and Sear: Sauté onions, garlic, spices, and tomato paste in olive oil. Sear the octopus for 5 minutes. You may need to club it to stop it from reciting the ancient deep one language.
Slow Cook: Add wine and tomatoes. Cover and simmer on low for 1.5 to 2 hours until tender.
Finish: Add potatoes and cook for 30 minutes until tender and sauce thickens, garnishing with parsley.

Tips for Success

Freeze the octopus beforehand to ensure it is tender and doesn’t fight back.
Let it simmer in its own juices—the octopus releases enough liquid without adding water.
Stir often to prevent the sauce from sticking and the tentacles from wrapping around you.

You can also try white wine/chorizo or make it Spanish-style with paprika.