Apex domains cannot have CNAME records.
Question and response
Question
dig yandex.net. NS
Answer
yandex.net. 4 NS ns2.yandex.net.
yandex.net. 4 NS ns1.yandex.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0