Preheat the oven to 180°C/350°F/gas 4.Discard any tough outer leaves from the cauliflower, then, keeping it whole, use a sharp knife to carefully slice a cross deep into the stalk so you can easily portion it up later.In a bowl, mix together the harissa, yoghurt, ½ a tablespoon of red wine vinegar and a little sea salt and black pepper, then quickly rub the mixture all over the cauli. Place it in a snug-fitting ovenproof frying pan or roasting tray.Halve the pomegranate and squeeze the juice of one half through a sieve over the cauli. Add 100ml of water at the base, and roast for 1 hour 15 minutes.When the time’s up, baste the cauli with the juices in the pan, then return to the oven for a final 10 minutes.Remove the pan, spoon the juices back over the cauli, then quickly sprinkle over the dukkah so it sticks.Holding the remaining pomegranate half cut-side down in your fingers, bash the back of it with a spoon so all the seeds tumble over the cauli, then halve or quarter, and dish up.