Apex domains cannot have CNAME records.
Question and response
Question
dig rozhled.net. NS
Answer
rozhled.net. 5 NS ns.rozhled.cz.
rozhled.net. 5 NS ns.rozhled.eu.
Authority
The response has no authority records.
Additional
ns.rozhled.cz. 5 A 5.180.200.2
ns.rozhled.eu. 5 A 93.185.111.178
ns.rozhled.cz. 5 AAAA 2a0b:3240:0:1:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0