Cut the octopus into 5cm pieces, take care to cut the small 'mouth' out of the very middle of the octopus, at the base of its head.
Add the octopus pieces to a large saucepan and place covered over medium-high heat (no liquid or oil required). After about 10 minutes uncover the saucepan and you will notice the octopus has started to release its juices. Let simmer with the lid off of 20 minutes or until the liquid has nearly all evaporated.
Add the red wine, olive oil and onions. Continue to cook over medium-high heat, stirring frequently, until the onions are soft.
Add the pasta sauce, salt and pepper then cover and simmer over a medium-low heat for 15 minutes. Uncover and continue to simmer for another 10 minutes if not enough water is evaporating from the sauce.
Once the octopus is tender, the sauce has thickened and the oil has risen to the surface of the sauce, remove from heat. Serve with your favourite pasta.