Apex domains cannot have CNAME records.
Question and response
Question
dig megacable.com.mx. NS
Answer
megacable.com.mx. 5 NS a26-65.akam.net.
megacable.com.mx. 5 NS a9-65.akam.net.
megacable.com.mx. 5 NS a4-64.akam.net.
megacable.com.mx. 5 NS a1-223.akam.net.
megacable.com.mx. 5 NS a11-64.akam.net.
megacable.com.mx. 5 NS a16-65.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0