Clean and wash the cauliflower, drain well and place in an ovenproof dish. Peel and finely chop the ginger. Mix tandoori paste, ginger, about half lemon juice and 200 g yoghurt. Season to taste with salt.
Coat the cauliflower with the yoghurt mixture and bake in a preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: see manufacturer) for approx. 1 hour.
Meanwhile, wash the mint and coriander, shake dry and pluck leaves from the stalks. Coarsely chop the leaves and, except for something to garnish, mix with 300 g yoghurt. Peel cucumber and grate finely.
Squeeze the grated cucumber and stir into the yoghurt, season with salt and pepper.
Remove cauliflower from the oven, sprinkle with remaining coriander and mint and serve with yoghurt.