Heat your oven to 220°C/Fan 200°C/Gas 7. Put a large roasting tin on the top shelf to heat up.
Break the cauliflower into small florets, discarding the leaves. Add to the warm roasting tin. Season well. Gloss with 1 tbsp oil. Roast for 15 mins till golden around the edges. Halve, peel and thinly slice the onion. Add it to the cauliflower. Roast for a further 10 mins or till everything’s tender.
While the veg cook, peel and finely chop the garlic. Finely chop the chilli, discarding the seeds and white bits.
Set a large pan over a high heat. Add 1 tbsp oil. Lower the heat. Stir in the garlic, chopped chilli and cinnamon stick. Sizzle for a mo. Add the passata and 250ml boiling water. Bring to the boil, then lower the heat. Simmer for 10 mins to thicken and tease out the cinnamon and chilli flavours.
Zest the lime. Remove the cinnamon stick from the tomato broth. Add the cauliflower, onion, lime zest and a squeeze of lime juice. Season to taste. Dish up into bowls. Serve with dukkah scattered on top.