Apex domains cannot have CNAME records.
Question and response
Question
dig uninet-ide.com.mx. NS
Answer
uninet-ide.com.mx. 4 NS nsmex2.uninet.net.mx.
uninet-ide.com.mx. 4 NS dnsadm-interno.uninet.net.mx.
uninet-ide.com.mx. 4 NS nsgdl2.uninet.net.mx.
uninet-ide.com.mx. 4 NS nsmty2.uninet.net.mx.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0