Some cakes formulas treat ground nuts as part of the flour/structure, while others treat the nuts as an “add-in,” so that they are not part of the structure of the cake. My recollection is that the golden almond cake (and the grand marnier cake that is modeled after it) use the nuts as part of the structure portion of the cake, but that the pistachio cake in RHC uses the ground pistachios as an add-in. I’m not sure about the wedding cake version, but I’ll try to take a look and post back. If the nuts are an add-in, they can be omitted with no problems. If they are part of the structure, then they would need to be replaced with something like half their weight in flour, and the fat portion of the formula would need to be checked to see if any increase is necessary.