Apex domains cannot have CNAME records.
Question and response
Question
dig ybaca.sk. NS
Answer
ybaca.sk. 5 NS ns02.ybaca.net.
ybaca.sk. 5 NS ns01.ybaca.net.
ybaca.sk. 5 NS ns03.ybaca.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0