Rinse lettuce, trim, spin dry and tear into small pieces. Rinse apples, quarter, core and dice finely. Cut roquefort into small pieces.
Peel onion and finely chop. Mix mayonnaise in a bowl with yogurt, lemon juice and onions and season to taste with paprika, salt, cayenne pepper and sugar.
Mix lettuce leaves in a bowl with apples and Roquefort, drizzle with yogurt mixture and season with paprika or cayenne pepper. Serve in bowls.