This is not a normal spike due to vst-gui handling. The graph shows that all cores are completely taken over for 100%. You should monitor the performance for a while, and keep the resource monitor open. Eventually you will see which proces is causing this behaviour. Uninstalling cubase will not solve the issue, since it seems that it is generated by another program.
You can also try: Process Explorer - Sysinternals | Microsoft Learn for monitoring.
kind regards,
R.