Apex domains cannot have CNAME records.
Question and response
Question
dig es.eu.org. NS
Answer
ES.EU.ORG. 5 NS NS.ANKH.FR.EU.ORG.
ES.EU.ORG. 5 NS NS1.EU.ORG.
ES.EU.ORG. 5 NS NS1.ERIOMEM.NET.
Authority
The response has no authority records.
Additional
ns1.eu.org. 5 A 45.63.100.187
ns1.eriomem.net. 5 A 136.244.111.41
ns1.eu.org. 5 AAAA 2001:19f0:7402:6b6:5400:1ff:fe9e:d9fe
ns1.eriomem.net. 5 AAAA 2a05:f480:1400:2c3f:5400:4ff:fef4:e48
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0