Apex domains cannot have CNAME records.
Question and response
Question
dig mnc.pl. NS
Answer
mnc.pl. 5 NS ns2.tpnets.com.
mnc.pl. 5 NS ns1.tpnets.com.
Authority
The response has no authority records.
Additional
ns1.tpnets.com. 5 A 193.151.112.10
ns2.tpnets.com. 5 A 193.151.112.20
ns1.tpnets.com. 5 AAAA 2001:1a68:15:0:0:0:0:10
ns2.tpnets.com. 5 AAAA 2001:1a68:15:0:0:0:0:20
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0