Apex domains cannot have CNAME records.
Question and response
Question
dig nic.plus. NS
Answer
nic.plus. 5 NS v0n0.nic.plus.
nic.plus. 5 NS v0n1.nic.plus.
nic.plus. 5 NS v0n2.nic.plus.
nic.plus. 5 NS v0n3.nic.plus.
nic.plus. 5 NS v2n0.nic.plus.
nic.plus. 5 NS v2n1.nic.plus.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0