Heat the oven to 220C (200C fan)/425F/gas 7. Tip the olive oil, baharat, salt, garlic, sweet potato, beetroot and chickpeas into a roasting tin large enough comfortably to hold all the vegetables in one layer. Mix well to coat – the chickpeas will fall under the veg, which is fine – then roast for 30 minutes.
Blanch the red onion in a bowl of boiling water for a minute, then drain well. Mix in the lemon juice and sea salt, then leave to pickle for 20 minutes.
Once the vegetables are out of the oven, dress them with the pickled onion/lemon mix, then taste and adjust the salt as needed. Scatter the feta and coriander over the top, and serve with some yoghurt alongside.