Apex domains cannot have CNAME records.
Question and response
Question
dig 2gis.ru. NS
Answer
2gis.ru. 4 NS ns.2gis.ru.
2gis.ru. 4 NS ns3.2gis.ru.
2gis.ru. 4 NS ns2.2gis.ru.
2gis.ru. 4 NS ns.2gis.tech.
Authority
The response has no authority records.
Additional
ns.2gis.ru. 4 A 91.236.51.51
ns2.2gis.ru. 4 A 91.236.50.7
ns2.2gis.ru. 4 A 91.236.50.171
ns3.2gis.ru. 4 A 91.221.199.133
ns3.2gis.ru. 4 A 212.20.27.10
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0