Apex domains cannot have CNAME records.
Question and response
Question
dig cvtsv.com. NS
Answer
cvtsv.com. 5 NS ns-654.awsdns-17.net.
cvtsv.com. 5 NS ns-1911.awsdns-46.co.uk.
cvtsv.com. 5 NS ns-243.awsdns-30.com.
cvtsv.com. 5 NS ns-1059.awsdns-04.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0