Apex domains cannot have CNAME records.
Question and response
Question
dig inext.net.mx. NS
Answer
inext.net.mx. 5 NS idcdns1.inext.net.mx.
inext.net.mx. 5 NS idcdns2.inext.net.mx.
inext.net.mx. 5 NS ns1.inext.net.mx.
Authority
The response has no authority records.
Additional
ns1.inext.net.mx. 5 A 200.52.138.68
idcdns1.inext.net.mx. 5 A 200.76.111.250
idcdns2.inext.net.mx. 5 A 200.76.111.251
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0