Apex domains cannot have CNAME records.
Question and response
Question
dig axtel.com.mx. NS
Answer
axtel.com.mx. 4 NS ns-gdl.axtel.net.
axtel.com.mx. 4 NS ns-mex.axtel.net.
axtel.com.mx. 4 NS ns-mty.axtel.net.
Authority
The response has no authority records.
Additional
ns-gdl.axtel.net. 4 A 201.163.58.5
ns-mex.axtel.net. 4 A 201.163.56.5
ns-mty.axtel.net. 4 A 201.163.57.5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0