Apex domains cannot have CNAME records.
Question and response
Question
dig city. NS
Answer
city. 5 NS v0n0.nic.city.
city. 5 NS v0n2.nic.city.
city. 5 NS v0n1.nic.city.
city. 5 NS v0n3.nic.city.
city. 5 NS v2n0.nic.city.
city. 5 NS v2n1.nic.city.
Authority
The response has no authority records.
Additional
v0n0.nic.city. 143758 A 65.22.24.4
v0n1.nic.city. 143758 A 65.22.25.4
v0n2.nic.city. 143758 A 65.22.26.4
v0n3.nic.city. 143758 A 161.232.12.4
v2n0.nic.city. 143758 A 65.22.27.4
v2n1.nic.city. 143758 A 161.232.13.4
v0n0.nic.city. 143758 AAAA 2a01:8840:1a:0:0:0:0:4
v0n1.nic.city. 143758 AAAA 2a01:8840:1b:0:0:0:0:4
v0n2.nic.city. 143758 AAAA 2a01:8840:1c:0:0:0:0:4
v0n3.nic.city. 143758 AAAA 2a01:8840:f6:0:0:0:0:4
v2n0.nic.city. 143758 AAAA 2a01:8840:1d:0:0:0:0:4
v2n1.nic.city. 143758 AAAA 2a01:8840:f7:0:0:0:0:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0