Just checking, no flour in the cake part? Just nuts, fat, and powdered sugar?

I've not made that particular cake, but have done similar nut based ones. Although we tend to think of flour as strictly a wheat product, in this case the ground nuts and powdered sugar are acting as stand-ins. This one uses pistachios, but there are many others using other types of nuts. The powdered sugar also contains a bit of cornstarch, which helps stabilize the structure as well. It will make a dense, but moist cake, no wheat flour needed.