Pre-heat the oven at 170 degrees for at least 15 minutes. Grease and line 8 inch pan and set it aside.
In a bowl, sieve together, all purpose flour, unsweetened cocoa powder, coffee powder, baking soda, baking powder and salt. Set it aside.
Mix together milk and vinegar and set it aside for 10 minutes.
In another bowl, add melted butter and sugar, whisk it until combined.
Add prepared milk and vinegar mixture and vanilla essence, give it a whisk.
Then, add half of the flour mixture and mix.
Add hot water and whisk again to combine every thing.
Add remaining flour mixture and give a gentle mix. Do not over mix the batter.
Pour the batter into prepared tin and place it in the middle rack of the oven.
Bake it in pre-heated oven for 35-40 minutes or until the tooth pick comes out clean.
Let the cake cool in tin for 15 minutes. Then, unmold and cool on wire rack completely.