The MacOS Install option in the MacOS Recovery screen will download a MacOS Installer for the version of MacOS that the computer was shipped with.

This is the the easiest option if one has a recent Mac with disabled permissions for boot from external media. As in that case it is not possible to reboot into the Startup Manager to choose an alternate boot option.

Select Install MacOS from the main menu in the Recovery screen and follow all the prompts.

Note: if you need to disable remote management, ensure the MacOS is disconnected from the internet after at the end of the install wizard process and before the computer reboots.