Apex domains cannot have CNAME records.
Question and response
Question
dig istv.uz. NS
Answer
istv.uz. 5 NS ns2.istv.uz.
istv.uz. 5 NS ns.istv.uz.
istv.uz. 5 NS ns01.uzsci.net.
Authority
The response has no authority records.
Additional
ns.istv.uz. 5 A 31.135.208.2
ns01.uzsci.net. 5 A 83.69.129.4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0