Apex domains cannot have CNAME records.
Question and response
Question
dig nic.mx. NS
Answer
nic.mx. 5 NS a.nic.mx.
nic.mx. 5 NS b.nic.mx.
nic.mx. 5 NS c.nic.mx.
nic.mx. 5 NS c.mx-ns.mx.
nic.mx. 5 NS m.mx-ns.mx.
nic.mx. 5 NS o.mx-ns.mx.
Authority
The response has no authority records.
Additional
c.mx-ns.mx. 144886 A 192.100.224.1
m.mx-ns.mx. 52838 A 200.94.176.1
o.mx-ns.mx. 96702 A 200.23.1.1
c.mx-ns.mx. 144886 AAAA 2001:1258:0:0:0:0:0:1
m.mx-ns.mx. 52838 AAAA 2001:13c7:7000:0:0:0:0:1
o.mx-ns.mx. 96702 AAAA 2001:1201:0:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0