If you try to add a CNAME record for the zone apex (root level or @), the following error message will be displayed:
Invalid attribute value; cannot create CNAME record - zone already has records
This is because CNAME records cannot be added to the root zone.
The two most common, easy-to-implement alternatives are A or AAAA records, or setting up web redirects instead.
A or AAAA Records
By adding an A (IPv4) or AAAA (IPv6) record pointing to the address that the target of the CNAME will ultimately resolve to.
This can be easily done from your Control Panel or via the UpdateDNSZone command.
Web Redirects
By setting up a redirect, also known as web forwarding. This can also be done from your Control Panel (the Forwardings tab):