Beat the eggs with the sugar in a large container, then add the oil, again beating until the mixture homogenizes. Next add the yoghurt and stir again.
Pour 1/2 the mixture into an oiled and floured cake form, add the cocoa to the other 1/2 and stir. Pour cocoa mixture in the middle of the white mixture and all around its circumference.
Put the cake to bake in a preheated 347°F (175 °C) oven about 45 min.