Apex domains cannot have CNAME records.
Question and response
Question
dig alfanet24.pl. NS
Answer
alfanet24.pl. 5 NS ns1.an24.pl.
alfanet24.pl. 5 NS ns2.an24.pl.
Authority
The response has no authority records.
Additional
ns1.an24.pl. 5 A 195.88.28.35
ns2.an24.pl. 5 A 195.88.28.36
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0