Apex domains cannot have CNAME records.
Question and response
Question
dig dacc.cz. NS
Answer
dacc.cz. 5 NS ns2.dacc.cz.
dacc.cz. 5 NS ns1.dacc.cz.
Authority
The response has no authority records.
Additional
ns1.dacc.cz. 5 A 89.22.67.3
ns2.dacc.cz. 5 A 165.232.153.110
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0