Apex domains cannot have CNAME records.
Question and response
Question
dig es.net. NS
Answer
es.net. 5 NS adns1.es.net.
es.net. 5 NS adns2.es.net.
Authority
The response has no authority records.
Additional
adns1.es.net. 5 A 192.188.22.22
adns2.es.net. 5 A 192.188.22.52
adns1.es.net. 5 AAAA 2001:400:ffff:ffff:ffff:0:0:4444
adns2.es.net. 5 AAAA 2001:400:ffff:ffff:ffff:0:0:8052
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0