I must thank my dear friend Sarita Wadhwani for the recipe for this lovely spongy eggless marble cake. It was very kind of her to post both the recipe and pic for all of us.
INGREDIENTS:

1 cup butter
1 small tin condensed milk-
2 cups of self raising flour
2 tsp soda bicarbonate
1 tsp baking powder –
a few drops of vainilla essence –
1/4 cup cadbury drinking chocolate –
1 /4cup cocoa powder
juice of 1and half oranges.
METHOD:
Mix butter and condensed milk
Add the flour
Add soda n baking powder n vanilla essence and 1 quater cup of warm water and  the orange juice .ç
When properly mixed put half of the mixture  in the baking tray and  in the other half of the batter  mix the cocoa n cadbury chocolate powder ..mix properly n pour on top of the other one ……bake in a preheeated oven for 15 mins on 175 degres n rest 45 mins on 150 degrees.