Apex domains cannot have CNAME records.
Question and response
Question
dig onfiber.com.mx. NS
Answer
onfiber.com.mx. 5 NS ns4.onfiber.com.mx.
onfiber.com.mx. 5 NS ns3.onfiber.com.mx.
onfiber.com.mx. 5 NS ns1.lapsoluciones.com.
onfiber.com.mx. 5 NS ns2.lapsoluciones.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0