Apex domains cannot have CNAME records.
Question and response
Question
dig agh.edu.pl. NS
Answer
agh.edu.pl. 5 NS nms.cyf-kr.edu.pl.
agh.edu.pl. 5 NS ns2.agh.edu.pl.
agh.edu.pl. 5 NS dns.fuw.edu.pl.
agh.edu.pl. 5 NS ns.icm.edu.pl.
agh.edu.pl. 5 NS ns1.agh.edu.pl.
Authority
The response has no authority records.
Additional
ns.icm.edu.pl. 5 A 212.87.14.39
dns.fuw.edu.pl. 5 A 193.0.80.11
nms.cyf-kr.edu.pl. 5 A 149.156.1.3
ns1.agh.edu.pl. 5 A 149.156.96.9
ns2.agh.edu.pl. 5 A 149.156.119.130
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0