Preheat the oven at 180*c..Take a big bowl and sift the flour, baking powder, baking soda and salt.take another bowl mix yogurt, sugar and oil in it..beat till sugar dissolves. Now add dry ingredients in it..whisk with electric beater or spatula..mix it gently till dry ingredients incorporated well. Add water if required..add vanilla Extract..same follow with other batter..add water in coco powder and add in other batter...

Take a cake loaf tin and grease it..add vanilla batter first at the bottom of the tin then pour the chocolate batter on it.alternatively add vanilla and chocolate cake batter, allowing to spread naturally. Using a back of spoon, give a zigzag swirl to get nice design.tapped the tin so that the batter settles down evenly with no gaps in between. Place the cake into the preheated oven. Bake the cake at 180 degree Celsius for 40 min.

Check the cake in middle to see if the baked with wooden toothpick..once done.let the cake rest in the tin.allow the cake tocool completely.later cut the cake into thick slices and serve.