Preheat the oven to 180°C and grease 2 x 20cm wide rectangular cake tins.
Beat butter and sugar together with an electric mixer until pale.
Add the coconut essence, then the eggs one at a time, beating well after each addition.
Add in the flour and baking powder and beat until just combined.
Divide the mixture between prepared tins and bake for 15-20 mins until lightly golden brown.
Cool on a wire rack before assembling.