Apex domains cannot have CNAME records.
Question and response
Question
dig nic.zone. NS
Answer
nic.zone. 5 NS v2n1.nic.zone.
nic.zone. 5 NS v0n1.nic.zone.
nic.zone. 5 NS v0n0.nic.zone.
nic.zone. 5 NS v0n2.nic.zone.
nic.zone. 5 NS v0n3.nic.zone.
nic.zone. 5 NS v2n0.nic.zone.
Authority
The response has no authority records.
Additional
v0n0.nic.zone. 50036 A 65.22.28.5
v0n1.nic.zone. 67322 A 65.22.29.5
v0n2.nic.zone. 67322 A 65.22.30.5
v0n3.nic.zone. 60779 A 161.232.14.5
v2n0.nic.zone. 60779 A 65.22.31.5
v2n1.nic.zone. 85083 A 161.232.15.5
v0n0.nic.zone. 50036 AAAA 2a01:8840:1e:0:0:0:0:5
v0n1.nic.zone. 67322 AAAA 2a01:8840:1f:0:0:0:0:5
v0n2.nic.zone. 67322 AAAA 2a01:8840:20:0:0:0:0:5
v0n3.nic.zone. 60779 AAAA 2a01:8840:f8:0:0:0:0:5
v2n0.nic.zone. 60779 AAAA 2a01:8840:21:0:0:0:0:5
v2n1.nic.zone. 85083 AAAA 2a01:8840:f9:0:0:0:0:5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0