Heat oven to 240C/220C fan/gas 7. Put the vegetables and chopped lemon in a large flameproof roasting tin and drizzle with 1 tbsp oil. Massage into the veg so they are all well coated, then put the tin on the hob and fry, stirring, for 5 mins until starting to char. Stir in two handfuls of the chickpeas, and roast in the oven for 15 mins. Put the rest of the chickpeas in a bowl with the garlic, tahini, yogurt, lemon juice and 3 tbsp water, and blitz with a stick blender until really smooth and thick. Spoon the yogurt tahini onto two plates and top with the roasted veg, pomegranate seeds and parsley. Season with black pepper and a drizzle of extra oil, if you like.