Mix ingredients A into a mixing bowl until combined. Whisk until light and fluffy.
In a separate bowl, whisk ingredients B until smooth and light. After that, add in ingredients C and D to the bowl. Mix until combined.
From the mixture of method (2), slowly incorporate into mixture from method (I).
Mix both mixtures until combined.
Prepare an 8-inch deep rectangular pan and butter the sides of the pan. Pour batter into the pan and smooth it out.
Preheat the oven to 170C and bake the cake for 45-50 minutes.