I assume you mean you have a ClusterCTRL Stack/Triple/Single when you say "not the rpi zero"?
If that is the case and the Pi running your NFS shares is connected via USB to the Cluster Stack controller you could set just the controller to auto power on and then use that to power on the other Pi once it has booted.
On the NFS server (controller).
Shutdown and then "clusterctrl off pX" for everything other than the controller Pi.
"clusterctrl savepos ORDER" replacing ORDER with the order number from clusterctrl status output.
The Cluster Stack will now only auto power on that Pi and you can use the controller to power on the other Pi once it has booted.