Preheat the oven to 170oC. Line a 21cm x 21cm cake tin with parchment paper.
Sift the superfine wholegrain flour, cake flour and baking powder together.
In a mixing bowl with whisk attachment, combine eggs, cake emulsifier and water. Add sugar and the sifted flour mixture and mix on low speed for 1 minute to combine the ingredients. After 1 minute, scrap down the side of the mixing bowl.
Turn the mixer to high speed and mix for 8 minutes. Check for smooth and shiny texture.
Change the speed to low and gradually add in the melted butter for 1 minute. Fold mixture until it is even.
Pour the batter into the cake tin.
Bake at 170oC for 32 – 35 minutes until a skewer inserted in the center come out dry and clean.
Remove the cake from oven and let it cool for a few minutes.