Apex domains cannot have CNAME records.
Question and response
Question
dig mx4.timeweb.ru. NS
Answer
mx4.timeweb.ru. 5 NS ns1.timeweb.ru.
mx4.timeweb.ru. 5 NS ns3.timeweb.org.
mx4.timeweb.ru. 5 NS ns2.timeweb.ru.
mx4.timeweb.ru. 5 NS ns4.timeweb.org.
Authority
The response has no authority records.
Additional
ns1.timeweb.ru. 5 A 85.193.93.93
ns2.timeweb.ru. 5 A 85.193.93.85
ns3.timeweb.org. 5 A 217.78.234.130
ns4.timeweb.org. 5 A 139.45.249.139
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0