Mix the sour cream and creme fraiche with the powdered sugar and lemon juice. Dissolve the gelatine according to the instructions on the packet, then add and stir in. When the mass starts to thicken, fold in the whipped sweet cream. Put the cream in the refrigerator until it is completely firm.
Then puree the raspberries (possibly with a little sugar if necessary) and spread on the cream. Chill again until ready to eat.