Apex domains cannot have CNAME records.
Question and response
Question
dig coeficiente.net.mx. NS
Answer
coeficiente.net.mx. 5 NS ns2.coeficiente.net.mx.
coeficiente.net.mx. 5 NS ns1.coeficiente.net.mx.
Authority
The response has no authority records.
Additional
ns1.coeficiente.net.mx. 5 A 131.196.251.224
ns2.coeficiente.net.mx. 5 A 131.196.251.224
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0