Apex domains cannot have CNAME records.
Question and response
Question
dig kyivstar.net. NS
Answer
kyivstar.net. 5 NS ns21.kyivstar.net.
kyivstar.net. 5 NS ns20.kyivstar.net.
kyivstar.net. 5 NS ns22.kyivstar.net.
Authority
The response has no authority records.
Additional
ns20.kyivstar.net. 5 A 2.22.230.65
ns21.kyivstar.net. 5 A 95.101.36.64
ns22.kyivstar.net. 5 A 95.100.175.64
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0