Apex domains cannot have CNAME records.
Question and response
Question
dig rambler.com.pl. NS
Answer
rambler.com.pl. 5 NS rambler.com.pl.
rambler.com.pl. 5 NS rambler.bydgoszcz.pl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0