For the chocolate cake, separate the eggs and beat the egg whites with the sugar until stiff. Then beat the yolks together with the room-warm butter until fluffy.
Put the flour, cocoa and baking powder in a bowl and mix well. Fold the flour mixture into the yolk mixture, alternating with the beaten egg whites.
Grease a loaf pan and bake the cake at 160 °C hot air for about 1 hour.