Apex domains cannot have CNAME records.
Question and response
Question
dig idc.net.pl. NS
Answer
idc.net.pl. 5 NS ns1.in.net.pl.
idc.net.pl. 5 NS ns1.idc.net.pl.
idc.net.pl. 5 NS info.tarman.pl.
Authority
The response has no authority records.
Additional
ns1.in.net.pl. 5 A 89.234.211.3
ns1.idc.net.pl. 5 A 89.234.211.21
info.tarman.pl. 5 A 217.117.128.3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0