Take a big bowl and place a sieve on top. Add all-purpose flour, powdered sugar, unsweetened cocoa powder, salt, baking soda and coffee and sieve it.
In a small bowl mix together water, oil and vinegar and add it slowly to the dry ingredients and make a smooth, lump free batter.
Use cut and fold for 10-12 times to mix everything properly. Put the batter in the pan and tap2-3 times.
Place the pan with batter in pre-heated pan and cover. Cook on lowest flame for 35-40 minutes.
After 40 minutes check the cake by poking it with a toothpick, if toothpick comes out clean means it is ready.
Turn off the heat and let it cool down completely. Once cold flip it out on a plate.