Apex domains cannot have CNAME records.
Question and response
Question
dig ping0.ru. NS
Answer
ping0.ru. 5 NS mirelle.ping0.ru.
ping0.ru. 5 NS dns1.zolotoff.ru.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0