pfSense

Unable to provide "@" or empty string for hostname field in the Azure DNS dynamic DNS setup. Any other record works correctly (all text entered in to the box accurately creates the associated record inside of the apex domain). Thus, if you need an A or AAAA record in the apex it is impossible to do.

I learned this by doing:
Apex domain for zone: home.example.org
Hostname provided in settings: home.example.org (and home.example.org.)
Record created: home.example.org.home.example.org

It seems that the intention would be to provide "@" or an empty string so that the record can be created appropriately via the Azure APIs.