Apex domains cannot have CNAME records.
Question and response
Question
dig freeboard.cz. NS
Answer
freeboard.cz. 5 NS shean-ng.vshosting.cz.
freeboard.cz. 5 NS ns2.vshosting.cz.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0