Apex domains cannot have CNAME records.
Question and response
Question
dig PULNET.RU. NS
Answer
pulnet.ru. 2 NS ns1.pulnet.ru.
pulnet.ru. 2 NS ns2.pulnet.ru.
Authority
The response has no authority records.
Additional
ns1.pulnet.ru. 2 A 37.153.0.5
ns2.pulnet.RU. 2 A 37.153.1.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0