In a blender,add sugar,refined oil,egg ,curd..give it a good blend of 30 seconds.
In a jar only,add maida ,salt,vanilla essence and baking soda.Blend again for 15seconds.
Divide it in two equal parts.
Keep one part as it is.
In other part,add cocoa powder.
Now grease a tin.Add 1 tsp of white plain batter in the centre.
Next spoon of cocoa powder right in the centre of the white batter.
Finish both the batters following same procedure.
Make a design With a help a toothpick .Tap the tin once gently
Place it in cooker and bake for complete 55 mins on sim.
Cover the cooker with normal plate.
Let it cool and then enjoy the slices of marble cake!