Apex domains cannot have CNAME records.
Question and response
Question
dig an-net.ru. NS
Answer
an-net.ru. 5 NS ns2.an-net.ru.
an-net.ru. 5 NS ns4.an-net.ru.
Authority
The response has no authority records.
Additional
ns2.an-net.ru. 5 A 91.238.156.1
ns4.an-net.ru. 5 A 91.238.157.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0