Apex domains cannot have CNAME records.
Question and response
Question
dig ientc.net.mx. NS
Answer
ientc.net.mx. 5 NS ns-344.awsdns-43.com.
ientc.net.mx. 5 NS ns-668.awsdns-19.net.
ientc.net.mx. 5 NS ns-1510.awsdns-60.org.
ientc.net.mx. 5 NS ns-1969.awsdns-54.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0