Preheat the oven to 180°C.
Remove the leaves of the cauliflower and line a baking dish with them.
Cut the onion into thin wedges, the red pepper into thin slices, the courgette into disks.
Tear the cauliflower florets off its stem and scatter these on top of the leaves together with the onion, cherry tomatoes, courgette and pepper pieces.
Lightly smash the garlic cloves, then tuck these between the vegetables.
Dust with the herbs, salt and pepper, then drizzle with oil and vinegar.
Bake in the oven for about 20 minutes, or until tender.
Pour over the passata, combine gently, then bake for a further 10 minutes or so, until the vegetables are lightly caramelized.
Serve warm with chopped parsley leaves.