Beat sugar and butter until fluffy.

One by one add the eggs

Fold in the flour and the baking powder, sifted together

Divide the batter into two equal parts.

Add the cocoa to one side

Pour the plain batter into 26 cm. greased and floured cake pan. With a spatula add the cocoa batter on top. Merge the the mixtures carefully using a knife to obtain the marble effect.

Bake for 30 minutes in 210 Celsius preheated oven.