Mix mayonnaise, yoghurt, mustard, vinegar and sugar to a salad dressing, season with salt and pepper.
Clean and wash the cauliflower and cut it into small florets. Roast the hazelnuts in a pan without fat, take them out, let them cool down and chop them roughly. Clean the lettuce, remove the stalk, wash the leaves, dab dry and cut into strips about 1 cm wide.
Wash, quarter and core the apples and cut them into bite-sized pieces.
Mix cauliflower, nuts and apples, arrange on plates and drizzle with salad dressing. Sprinkle with lettuce.