Pluck basil and thyme leaves and chop finely. Mix yoghurt, crème fraîche, milk and lemon juice. Mix in herbs and lemon peel. Season with salt, pepper and 1 pinch of sugar.
Clean, wash, spin dry and pluck lettuce into bite-sized pieces. Peel red onion and cut into rings. Wash, halve and core the apple and cut it into thin slices. Wash tomatoes and cut into slices.
Mix lettuce, tomatoes, apple and onion with the dressing and serve immediately.