Apex domains cannot have CNAME records.
Question and response
Question
dig dragon.cz. NS
Answer
dragon.cz. 5 NS ns.dragon.cz.
dragon.cz. 5 NS ns1.dragon.cz.
Authority
The response has no authority records.
Additional
ns.dragon.cz. 5 A 213.168.176.53
ns.dragon.cz. 5 AAAA 2a02:13b8:0:53:0:0:0:53
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0