Whip the egg yolks with softened butter and sugar till foamy. Slowly mix in sour cream, flour, raisins, lemon rind and salt. Let the mixture stand for 15 minutes.
Whip the egg whites till they form peaks. Sieve the cottage cheese and gently fold into the egg whites. Mix this with the first mixture.
Sprinkle the semolina on the prepared sheet of strudel d