Heat oven to 190C/170C fan/gas 5. Halve the aubergine lengthways and score the flesh side deeply, brush with a good layer of olive oil and put on a baking sheet. Roast for 20 mins or until the flesh is soft enough to scoop out.
Fry a finely chopped onion in a little oil until soft, add 2 crushed garlic cloves and 1 tsp cinnamon and fry for 1 min. Once the aubergines are cool enough to handle, scoop out the centres. Roughly chop the flesh and add it to the onions. Halve 3 tomatoes, scoop the seeds and juice into a sieve set over a bowl, then chop the flesh. Add the chopped tomatoes to the pan and cook everything for 10 mins until nice and soft. Add a little more oil if you need to. Stir in some chopped parsley, leaving a little for scattering at the end.
Lay the aubergine halves in a baking dish and divide the tomato mixture between them. Pour over the juice from the tomatoes, drizzle with more olive oil and bake for 30 mins until the aubergines have collapsed.
Meanwhile, mix the tzatziki ingredients together. One should use fresh mint, but I had used the last from our garden earlier this week. So I used Greek yoghurt, a tsp mint sauce from a pot. Then took 6 cm of a cucumber, scooped the seeds out and grated the rest to add to the mix. Put in 2 small serving bowls.
Season the lamb with salt, black pepper and a pinch of paprika. Griddle, grill or barbecue for 3 mins on each side or until the fat is nicely browned, then put in a serving dish and squeeze over the lemon halves. Scatter the aubergines with parsley, then serve with the lamb and tzatziki.