Apex domains cannot have CNAME records.
Question and response
Question
dig seravo.com. NS
Answer
seravo.com. 5 NS z.dns.gandi.net.
seravo.com. 5 NS ns-4-b.gandi.net.
seravo.com. 5 NS ns-21-c.gandi.net.
seravo.com. 5 NS ns-141-a.gandi.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0