Apex domains cannot have CNAME records.
Question and response
Question
dig iwao.cz. NS
Answer
iwao.cz. 2 NS ns.wedos.com.
iwao.cz. 2 NS ns.wedos.net.
iwao.cz. 2 NS ns.wedos.cz.
iwao.cz. 2 NS ns.wedos.eu.
Authority
The response has no authority records.
Additional
ns.wedos.cz. 2 A 45.138.106.1
ns.wedos.cz. 2 A 185.8.238.1
ns.wedos.eu. 2 A 185.8.238.0
ns.wedos.com. 2 A 45.138.106.0
ns.wedos.net. 2 A 75.2.92.86
ns.wedos.net. 2 A 99.83.142.9
ns.wedos.cz. 2 AAAA 2a0e:acc0:1:0:0:caff:caff:cafb
ns.wedos.cz. 2 AAAA 2a0e:acc0:2:0:0:c:1:c1
ns.wedos.eu. 2 AAAA 2a0e:acc0:2:0:0:b:1:b1
ns.wedos.com. 2 AAAA 2a0e:acc0:1:0:0:cafe:cafe:cafe
ns.wedos.net. 2 AAAA 2600:9000:a705:25bb:c632:5e5a:dd9c:1e46
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0