Beat the eggs with an electric mixer for 1 minute.

Add vanilla and vinegar to the eggs and beat again.

Add oil, milk and sugar; beat for another minute.

In a separate bowl, mix together the flour, baking powder and salt.

Make a whole in the middle of the dry ingredients and add the liquid mixture to it. Beat for 1 minute.

Separate the batter in half; now you have 2 bowls with half the batter in each.

In one bowl, add cocoa powder and mix till it’s “chocolaty”.

Spray a pan with cooking spray, add half the white batter to the pan, then add all the chocolate batter then add the rest of the white batter on top.

Move a knife in between the layers so that you have a marble effect.

Preheat oven on medium heat (275 degrees) and bake the cake for 25 minutes or until a toothpick inserted comes out clean.