Apex domains cannot have CNAME records.
Question and response
Question
dig grupozil.com. NS
Answer
grupozil.com. 5 NS ns-1846.awsdns-38.co.uk.
grupozil.com. 5 NS ns-1554.awsdns-02.co.uk.
grupozil.com. 5 NS ns-838.awsdns-40.net.
grupozil.com. 5 NS ns-906.awsdns-49.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0