Grease and flour the gugelhupf form (bundt cake pan).
Wash the rhubarb and cut into pieces.
Beat egg whites, salt and half of the sugar until stiff.
Beat butter with remaining sugar until creamy and light.
Stir in yolks, one by one.
Mix flour and baking powder and fold into the butter mixture with the beaten egg whites.
Fold in the single cream.
Mix rhubarb pieces with sugar and coconut flakes.
Fold into the batter.
Pour into the prepared gugelhupfform (bundt pan).
Bake in the preheated oven at 170° C for about 60 - 65 minutes. (test with toothpick)
After about 10 minutes, remove from the form and leave to cool completely on a cooling rack.