Mix all the ingredients well, except for the cocoa, until fluffy. Then 2/3 of the dough can be put into a greased ring tin. Mix the remaining 1/3 of the dough with the cocoa and pour onto the light dough. To get the marbling, the dark mass can be easily pulled through the light dough with a fork. Now the cake can be baked at 175 °C for about 50-60 minutes.