Preheat oven to 177 degree C . Grease your loaf pan and line the bottom with parchment paper. Well, I used a silicone loaf pan, so didn't have to go through this step.
n a bowl, mix cocoa powder with the hot water till it is smooth and lump free. Set aside to cool completely.
In another bowl, sift together flour, corn flour, salt and baking powder.
Using your hand mixer or stand mixer whisk butter till smooth and creamy. Add sugar to this and continue beating till the mixture is fluffy and light( about 2-3 mins). Drop in the eggs one by one, beating after each addition.
Now add the vanilla extract and the cocoa mixture and beat till incorporated.
Tip in the flour mixture and using a rubber spatula, fold it into the butter mixture until just combined. Do not over mix.
Pour the batter into the prepared pan and bake for 50-55 mins or till a toothpick inserted into the centre of the cake comes out clean.
Cool completely before slicing.