Soak the gelatine in cold water and then heat and dissolve in a saucepan. Drain the pineapple slices and cut into small pieces. Beat a thick cream with the sugar and pineapple juice and stir in the dissolved gelatine.
Wash the lemons with hot water, dry them and rub the peel into the cream. Stir half of the pineapple pieces into the cream.
Stir the cream quark and crème fraîche until smooth and also mix into the cream.
Whip the cream with vanilla sugar until stiff and stir in as soon as the cream begins to set. Leave to set in the refrigerator for 3 hours.
Before serving, decorate the cream with the remaining pineapple pieces.