Clean the rhubarb, wash and pat dry. Cut rhubarb lengthwise into halves or quarters and dice (625 g net).
Separate 4 eggs, chill the egg white. Mix the fat, 100 g sugar, 2 packets of vanillin sugar and salt with the whisks of the hand mixer for about 5 minutes until creamy. Stir in egg yolks one after the other. Then add 3 eggs alternating with 1 tbsp. flour each and stir in.
Mix the remaining flour and baking powder and stir in briefly with the cream.
Grease a springform pan (30 cm Ø) and dust with flour. Put the dough into the form and smooth it down. Mix 250 g rhubarb and 1 tbsp. sugar, spread on the dough. In the preheated oven, 2.
Bake from below (electric oven: 175 °C/ circulating air: 150 °C/ gas: see manufacturer) for about 20 minutes.
Beat the egg whites until stiff, adding 200 g sugar and 1 sachet of vanillin sugar at the end. Dust 375 g rhubarb with starch and mix. Fold the rhubarb into the meringue. Remove the cake from the oven.
Spread the rhubarb meringue loosely, leaving a 2-3 cm wide edge all around.
Put the cake back into the hot oven and bake in about 35 minutes. Take out and place on a cake rack. Carefully remove the cake from the rim with a sharp knife, remove the rim of the mould and let the cake cool down.
Lift the cake onto a cake plate and dust the edge with icing sugar. Whipped cream tastes good with it.