Peel the fresh rhubarb and cut into small cubes (approx. 1 to 1.5 cm).
Put butter / margarine, eggs, salt, sugar and vanilla sugar in a bowl and beat until frothy for about 3 minutes. Then mix in the flour and baking powder and stir again. Finally add the rhubarb and chocolate cubes and fold in well.
Pour the dough into a loaf pan and bake for about 60 minutes at 180 ° C in the preheated oven until the cake is golden brown.
I always line the loaf pan with baking paper, so I save myself grease and can easily lift the cooled cake out of the pan.