Apex domains cannot have CNAME records.
Question and response
Question
dig lumenet.com.mx. NS
Answer
lumenet.com.mx. 5 NS ns3.lumenet-comunicaciones.com.
lumenet.com.mx. 5 NS ns1.lumenet-comunicaciones.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0