This cake is one I saw on a great cooking show, Good Chef, Bad Chef , I recommend using both almond extract and amaretto (Yum). I think another good combination would be rose water and vanilla.
You must check the cake with a skewer and make sure it comes out clean, mine takes a little longer than the recipe says. I also put the juice of a half a lime over the cake when it came out of the oven - make it taste even better. I also used almond slivers instead of flakes as they are a bit crunchier, seem to match the pistachios better.
Its an easy, gluten free cake that tastes wonderful!