Apex domains cannot have CNAME records.
Question and response
Question
dig ptr.network. NS
Answer
ptr.network. 4 NS ns1.reg.ru.
ptr.network. 4 NS ns2.reg.ru.
Authority
The response has no authority records.
Additional
ns1.reg.ru. 1 A 176.99.13.11
ns1.reg.ru. 1 A 176.99.13.13
ns1.reg.ru. 1 A 176.99.13.15
ns1.reg.ru. 1 A 176.99.13.17
ns1.reg.ru. 1 A 194.58.117.11
ns1.reg.ru. 1 A 194.58.117.13
ns1.reg.ru. 1 A 194.58.117.15
ns1.reg.ru. 1 A 194.58.117.17
ns2.reg.ru. 1 A 176.99.13.12
ns2.reg.ru. 1 A 176.99.13.14
ns2.reg.ru. 1 A 176.99.13.16
ns2.reg.ru. 1 A 176.99.13.18
ns2.reg.ru. 1 A 194.58.117.12
ns2.reg.ru. 1 A 194.58.117.14
ns2.reg.ru. 1 A 194.58.117.16
ns2.reg.ru. 1 A 194.58.117.18
ns1.reg.ru. 1 AAAA 2a00:f940:9:0:0:0:1:1
ns1.reg.ru. 1 AAAA 2a00:f940:9:0:0:0:2:1
ns2.reg.ru. 1 AAAA 2a00:f940:9:0:0:0:1:2
ns2.reg.ru. 1 AAAA 2a00:f940:9:0:0:0:2:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0