Place all dry ingredients (cocoa powder, flour, salt, sugar and baking powder) into a small bowl or cup and stirring until complete mixing. Add the wet ingredients (sunflower oil, coffee or milk) and stirring continues until the mixture is homogeneous. Place the cup or bowl in the microwave on full power for 40-45 seconds or more, according to the desired firmness of the cake and the power of the MB. After the first 30 seconds the cup can be rotated in order to avoid any unilateral heating of the appliance. Allow to cool for a few seconds, and then sprinkle top with sugar, chocolate topping or another.