Tunisian Octopus

Discovery of this dish was, for me, an unintended consequence of buying Octopus rather than Squid in the supermarket, about a month ago. The Technical Dept took the opportunity to make some comment to the effect that I should wear my glasses more often - the sort of unnecessary remark which should not be dignified by being noticed - but in fact I put it down rather to the 'Stepford Wives' effect that takes hold whenever I enter any supermarket anywhere: the brain closes down, I glaze over, and I go into autopilot.
Anyway...Octopus. I contemplated ploughing on with the intended menu, and pretending that Squid and Octopus are interchangeable, although I know they aren't (generally) and that I risked a much tougher end-result than intended, and then resorted instead for inspiration to Alan Davidson's 'Mediterranean Seafood'. (Actually, I don't know why I say 'resorted', since it is a splendid volume...I suppose because I have a misplaced tendency to regard it as a reference book rather than a book for general browsing.) And I came across this recipe, which is quite simply delicious. And so easy, it barely warrants being called a 'recipe'.
I serve it on a bed of rocket, which cuts the richness and spiciness of the sauce, but I imagine it would do just as well as a pasta sauce, or else stirred (at the end) into a plain risotto bianco.

Sufficient for two generous servings.
Ingredients: 1 Octopus, about 1 kg in weight, and thoroughly cleaned and prepared; 1 onion; Olive Oil; Seasoning; 1 tbs Tomato Purée; 1 tsp Chili Powder (or harissa); 2 tsps ground Cumin.

Method:
1. In a couple of tablespoons of oil, gently sauté the finely chopped Onion for a minute or so.

2. Chop the body and tentacles of the Octopus into half-inch peces, then add to the pan, along with salt and pepper. Cook over medium heat for a few minutes, stirring, until they begin to take colour.

3. Mix the tomato purée and chili powder with a cup of water, and add this to the pan. Continue to cook, stirring from time to time for ten minutes. Then, add enough water to cover, bring to the boil, and then reduce to a low simmer, cover the pan, and leave simmering for an hour and a quarter.

4. Add to the pan the ground cumin, and continue to simmer for a further 15 minutes. Taste and adjust seasoning as necessary.

Serve immediately, in your preferred form, or else leave to serve later, after having reheated over a low heat for about ten minutes.