Apex domains cannot have CNAME records.
Question and response
Question
dig netservis.cz. NS
Answer
netservis.cz. 5 NS doyle.netservis.cz.
netservis.cz. 5 NS bodie.netservis.cz.
Authority
The response has no authority records.
Additional
bodie.netservis.cz. 5 A 82.208.18.197
doyle.netservis.cz. 5 A 81.0.235.48
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0