Preheat oven to 180˚C. Brush a 25cm x 30cm shallow cake tin with melted butter. Line cake base with baking paper.
Combine all ingredients except pistachios in a mixing bowl and mix all by using an electric mixer for 2 minutes on low speed then mix on high speed for another 3 minutes.
Add half cup of pistachios into this mixture and mix on low speed for 1 minute.
Pour mixture into prepared pan, spread other ½ cup of pistachio on top and put in oven for 20-25 minutes or until a skewer comes out clean if inserted in the center.
