Apex domains cannot have CNAME records.
Question and response
Question
dig gmmexicali.com. NS
Answer
gmmexicali.com. 3 NS ns1.lumenet.com.mx.
gmmexicali.com. 3 NS ns2.lumenet.com.mx.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0