This is one of my favorite suppers, although there's nothing that says you can't serve this as a vegetable side as part of a more conventional meal. And you could also bolster it further by crumbling in some feta. But for me, it is perfect just as it is: the tomatoes almost ooze into a dressing in the oven, and the cauliflower softens, but not soggily. For choice, I'd always use home-cooked chickpeas (I cook batches in my slow cooker and freeze them in 1 1/2-cup portions for everyday use), but otherwise I like the pre-cooked Spanish chickpeas in jars. Yes, they are more expensive than the canned variety, but the cheapest option is always to buy dried. Don't feel bad about using chickpeas out of a can, though--I have been known to, myself. One can't always be so organized to have the freezer stashed with cooked chickpeas, and so I am always well stocked with canned chickpeas. They do work here, it's just that they won't be as soft; but then, you don't necessarily need them to be. The cauliflower and juicy tomatoes can stand some nubbliness.
The parsley is not a garnish--ugh, that word--but used, here, as a salad leaf. And this is also very, very good cold, so if you have some left over, it makes a fabulous box lunch, or provides instant gratification on those days you have to eat fridge-side, with your coat still on, you're so hungry.
Preheat the oven to 220 degrees C (425 degrees F)/gas mark 7. Trim the cauliflower and divide into small florets. Pour the oil into a large bowl, add the cinnamon and cumin seeds, and stir or whisk to help the spices disperse. Tip in the prepared cauliflower and toss to coat. Pour the contents of the bowl into a small oven tray (I mostly use a disposable foil baking tray measuring 30-by-20 centimeters [12-by-8 inches]) and place in the oven for 15 minutes. Don't wash out the bowl you've been using just yet.
Add the chickpeas to this bowl, and add the harissa, tasting it first to see if you want both tablespoonfuls, and, at the risk of being repetitive, toss to coat. Quarter the tomatoes and add them to the bowl, and shake or stir to mix. When the cauliflower has had its 15 minutes, remove the tray, quickly tip the chickpeas and tomatoes over the cauliflower, and toss to combine before returning to the oven for a further 15 minutes until the cauliflower is tender.
When it's ready, remove from the oven and sprinkle the salt over the vegetables, then (and this isn't the last time) toss to combine with half of the pomegranate seeds before dividing between 2 bowls. Divide the parsley leaves--without chopping them--between the 2 bowls and toss to mix. Scatter with the remaining pomegranate seeds.
Cool leftovers, then cover and refrigerate within 2 hours of making. Will keep in fridge for up to 2 days. Serve cold.