You can use the erase subcommand with the --core parameter to determine what memory and which UICR page is erased. For multi-core devices, this means that a single execution of the erase subcommand might not erase the whole memory, and multiple calls are required to erase the memory for all cores.
When using the --core parameter, make sure the core is available on your device.
This parameter is useful if the core has specific programmable memory assigned to it, as this parameter also implicitly selects the programmable memory, for example on nRF53 Series devices. If the cores on the device share the programmable memory, like on nRF54H Series devices, this parameter is not required.