Apex domains cannot have CNAME records.
Question and response
Question
dig eu. NS
Answer
eu. 5 NS x.dns.eu.
eu. 5 NS w.dns.eu.
eu. 5 NS y.dns.eu.
eu. 5 NS be.dns.eu.
eu. 5 NS si.dns.eu.
Authority
The response has no authority records.
Additional
w.dns.eu. 169640 A 194.0.25.28
x.dns.eu. 169662 A 185.151.141.1
y.dns.eu. 169690 A 194.146.106.90
be.dns.eu. 47510 A 149.38.1.26
si.dns.eu. 172250 A 193.2.221.62
w.dns.eu. 169640 AAAA 2001:678:20:0:0:0:0:28
x.dns.eu. 169662 AAAA 2a02:568:fe00:0:0:0:0:6575
y.dns.eu. 169690 AAAA 2001:67c:1010:23:0:0:0:53
si.dns.eu. 172250 AAAA 2001:1470:8000:100:0:0:0:62
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0