dns root came
Feature Request - DNS zone root apex alias capability in Windows Server DNS
This would allow a customer to direct requests to the root of an DNS hosted zone (e.g. mydomain.com) to cdn/hosted services. This is required because a CNAME alias is not a supported record type for the apex root (@) record in a DNS zone.
Azure supports this, so not sure why windows server team didn't implement this as well:
AWS Route 53 DNS service gets around this using the concept of an alias which allows the root apex record of a DNS zone to point to cdn/cloud hosted services.