Apex domains cannot have CNAME records.
Question and response
Question
dig solver.net.ua. NS
Answer
solver.net.ua. 5 NS ns.secondary.net.ua.
solver.net.ua. 5 NS ns.solver.net.ua.
Authority
The response has no authority records.
Additional
ns.solver.net.ua. 5 A 194.44.39.130
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0