Apex domains cannot have CNAME records.
Question and response
Question
dig rhscz.eu. NS
Answer
rhscz.eu. 5 NS ns2.he.net.
rhscz.eu. 5 NS ns1.rhscz.eu.
rhscz.eu. 5 NS ns1.he.net.
rhscz.eu. 5 NS ns2.rhscz.eu.
Authority
The response has no authority records.
Additional
ns1.he.net. 5 A 216.218.130.2
ns1.rhscz.eu. 5 A 144.21.42.190
ns2.he.net. 5 A 216.218.131.2
ns2.rhscz.eu. 5 A 193.123.34.149
ns1.he.net. 5 AAAA 2001:470:100:0:0:0:0:2
ns1.rhscz.eu. 5 AAAA 2603:c022:c003:5500:0:0:1:2
ns2.he.net. 5 AAAA 2001:470:200:0:0:0:0:2
ns2.rhscz.eu. 5 AAAA 2603:c022:c003:5500:0:0:1:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0