Apex domains cannot have CNAME records.
Question and response
Question
dig mikrohosting.cz. NS
Answer
mikrohosting.cz. 4 NS dns1.it-help.cz.
mikrohosting.cz. 4 NS dns.it-help.cz.
mikrohosting.cz. 4 NS dns2.it-help.cz.
Authority
The response has no authority records.
Additional
dns.it-help.cz. 4 A 194.108.42.2
dns1.it-help.cz. 4 A 194.108.42.253
dns2.it-help.cz. 4 A 212.80.90.245
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0