Wash the rhubarb, cut into pieces and place on the bottom of the springform pan. Mix the fat with sugar until frothy and gradually add the eggs, flour, cornstarch and baking powder. Spread the dough on the rhubarb and bake at 170 ° C for about 40 minutes. Let cool down for approx. 5 minutes after baking. Then turn out onto a cake plate and dust with powdered sugar.