Cook the cauliflower until soft.
Combine yoghurt and ajvar in a bowl (if using) and set aside.
Meanwhile preheat a nonstick pan over medium heat.
Fry bell pepper, onion, zucchini and aubergine until soft.
Preheat another nonstick pan and fry shrimps with the harissa for 3-4 minutes until done.
Drain the cauliflower and mix using a hand mixer until smooth.
Add lemon juice from 1/2 lemon, dijon mustard and salt and combine well.
Put the cauliflower pureé on a plate together with the fried shrimps and vegetables.
Sprinkle lemon juice on top.
Add some fresh basil (I also added some thick balsamic vinegar but thats optional).
Serve with ajvar sauce.