Apex domains cannot have CNAME records.
Question and response
Question
dig n1.os-ns.com. NS
Answer
n1.os-ns.com. 5 NS ns1.dns1.fleetservers.net.
n1.os-ns.com. 5 NS ns2.dns1.fleetservers.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0