Apex domains cannot have CNAME records.
Question and response
Question
dig nepustil.eu. NS
Answer
nepustil.eu. 5 NS ns1.nepustil.net.
nepustil.eu. 5 NS ns.nepustil.eu.
nepustil.eu. 5 NS ns.nepustil.de.
Authority
The response has no authority records.
Additional
ns.nepustil.de. 5 A 212.71.200.209
ns.nepustil.eu. 5 A 212.71.212.81
ns.nepustil.de. 5 AAAA 2001:14f8:8:0:0:0:0:1
ns.nepustil.eu. 5 AAAA 2001:14f8:7:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0