Preheat the oven to 180°C.
Peel the sweet potatoes then cut them into small chunks. Peel and cut the onion into wedges. Peel the garlic. Cut the pepper into chunks. Put them in a large baking dish, then scatter the cherry tomatoes around them. Add the cumin, coriander, salt and pepper, then drizzle with oil and toss. Bake for 20-25 minutes, until the vegetables are tender.
Meanwhile cook the pasta according to the packet instructions. Finley chop the cabbage and add it to the pasta for the last 2 minutes of cooking. Drain, pouring some of the cooking water into a small jug. Put the pasta and cavolo nero back into thee pan, and keep warm with a lid on.
When the roasted vegetables are cooked, pour everything, including the cooking jus, into a liquidiser and process it into a textured or smooth purée. Of it’s too thick, add some cooking water.
Mix the sauce with the pasta and cavolo nero. Add some more cooking water, if it’s too sticky.
Serve with plenty of the freshly ground pepper and some chilli flakes, if liked.