Preheat oven at 340 degrees F (170 degrees C).
Mix together All-Purpose Flour (3/4 cup), Unsweetened Cocoa Powder (1/4 cup), Powdered Confectioners Sugar (3/4 cup), and Baking Powder (1 teaspoon). Beat Egg (2), Sunflower Oil (1/2 cup), and Vanilla Essence (1 teaspoon). Combine this with the flour mix. Now add Water (1/2 cup) and combine.
Swiss Roll cake batter should be a little thinner than the normal cake batter. Cake should not rise too much, but should be soft too. For that hot water is added. Pour this to a rectanglar cake tin. I used a 15x10 centimeter cake tin. Bake for 15 to 20 minutes. Once done, take out and let it cool for 5 minutes.
Flip the cake on to a kitchen towel. Place a butter paper on top of the kitchen towel so that the cake won't stick on the towel. Now roll up the hot cake and keep it aside to cool well.
For filling: Beat the Whipping Cream (1/2 cup) until stiff. Add Orange Marmalade (1/2 cup) and Orange (1/2 teaspoon) and combine.
Once the cake is cooled well open the roll and spread the cream filling.
Roll it back again. Keep in fridge for some time and cut and serve.