91.200.239.0.ip.interplus.com.pl has no CNAME records.
Question and response
Question
dig 91.200.239.0.ip.interplus.com.pl. NS
Answer
The response has no answer records.
Authority
ip.interplus.com.pl. 3600 SOA dns1.interplus.com.pl. lukasz.itservice4u.pl. 2018110201 43200 900 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0