Apex domains cannot have CNAME records.
Question and response
Question
dig vtelecom.pl. NS
Answer
vtelecom.pl. 5 NS ns1.nette.pl.
vtelecom.pl. 5 NS ns3.vtelecom.pl.
Authority
The response has no authority records.
Additional
ns1.nette.pl. 5 A 193.138.118.3
ns3.vtelecom.pl. 5 A 46.232.128.244
ns1.nette.pl. 5 AAAA 2a02:2928:a:0:0:0:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0