Apex domains cannot have CNAME records.
Question and response
Question
dig mcm-telecom.com.mx. NS
Answer
mcm-telecom.com.mx. 4 NS dns.mcmtelecom.com.mx.
mcm-telecom.com.mx. 4 NS dns2.mcm.net.mx.
Authority
The response has no authority records.
Additional
dns.mcmtelecom.com.mx. 4 A 200.52.66.125
dns2.mcm.net.mx. 4 A 200.52.68.190
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0