Apex domains cannot have CNAME records.
Question and response
Question
dig skycloud.pl. NS
Answer
skycloud.pl. 5 NS ns2.skynet.net.pl.
skycloud.pl. 5 NS ns3.skynet.net.pl.
Authority
The response has no authority records.
Additional
ns2.skynet.net.pl. 1 A 194.153.119.5
ns3.skynet.net.pl. 1 A 194.153.119.5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0