Apex domains cannot have CNAME records.
Question and response
Question
dig SNBOX.RU. NS
Answer
SNBOX.RU. 5 NS arch.ns.cloudflare.com.
SNBOX.RU. 5 NS rafe.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0