Separate eggs. Beat the egg yolks, 3 tablespoons of water, 75 g sugar, vanillin sugar and lemon zest in a hot water bath until the sugar has dissolved. Continue beating cold until a firm cream is formed. Beat the egg whites until stiff and gradually add 50 g sugar. Mix flour, starch, almonds and baking powder. Fold the beaten egg white into the egg yolk mixture and fold in the flour mixture. Line the bottom of a springform pan (26 cm Ø) with baking paper.
Fill in the sponge cake mixture and smooth it down. Bake in the preheated oven (electric: 175 °C/ gas: level 2) for 25-30 minutes. In the meantime wash and clean the rhubarb. Remove the skin if necessary. Cut the rhubarb diagonally into pieces about 3 cm long. Heat 100 ml water with 100 g sugar and steam the rhubarb for 3-5 minutes. Remove and put aside. Soak the gelatine in cold water. Cut the vanilla pod in half lengthwise and scrape out the pulp. Simmer milk, 100 g cream, remaining sugar, vanilla pod and pulp for about 5 minutes. Squeeze the gelatine well and dissolve in the hot milk. Put it in a cold place and let it cool down while stirring occasionally. Remove sponge cake from the oven and let it cool down for about 10 minutes. Remove the springform pan and let it cool down completely.
Soak the gelatine in cold water. Cut the vanilla pod in half lengthwise and scrape out the pulp. Simmer milk, 100 g cream, remaining sugar, vanilla pod and pulp for about 5 minutes. Squeeze the gelatine well and dissolve in the hot milk. Put it in a cold place and let it cool down while stirring occasionally. Remove sponge cake from the oven and let it cool down for about 10 minutes. Remove the springform pan and let it cool down completely. Halve the sponge cake and stretch a cake ring around the bottom cake base. Whip 300 g cream until stiff. As soon as the milk mixture starts to gel, fold in the cream. Fold in 3/4 of the rhubarb. Pour the cream on the bottom cake layer and place the 2nd cake layer on top and chill for about 3 hours. Whip the rest of the cream until stiff and spread the cake as desired. Decorate the cake with the remaining rhubarb, pistachios and brittle
Halve the sponge cake and stretch a cake ring around the bottom cake base. Whip 300 g cream until stiff. As soon as the milk mixture starts to gel, fold in the cream. Fold in 3/4 of the rhubarb. Pour the cream on the bottom cake layer and place the 2nd cake layer on top and chill for about 3 hours. Whip the rest of the cream until stiff and spread the cake as desired. Decorate the cake with the remaining rhubarb, pistachios and brittle
Waiting time approx. 3 hours