Apex domains cannot have CNAME records.
Question and response
Question
dig grupoamasi.com. NS
Answer
grupoamasi.com. 5 NS ns-1897.awsdns-45.co.uk.
grupoamasi.com. 5 NS ns-1413.awsdns-48.org.
grupoamasi.com. 5 NS ns-1058.awsdns-04.org.
grupoamasi.com. 5 NS ns-1918.awsdns-47.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0