Apex domains cannot have CNAME records.
Question and response
Question
dig plus. NS
Answer
plus. 2 NS v0n0.nic.plus.
plus. 2 NS v2n0.nic.plus.
plus. 2 NS v0n1.nic.plus.
plus. 2 NS v0n3.nic.plus.
plus. 2 NS v0n2.nic.plus.
plus. 2 NS v2n1.nic.plus.
Authority
The response has no authority records.
Additional
v0n0.nic.plus. 155349 A 65.22.32.39
v0n1.nic.plus. 155349 A 65.22.33.39
v0n2.nic.plus. 170658 A 65.22.34.39
v0n3.nic.plus. 155349 A 161.232.16.39
v2n0.nic.plus. 170658 A 65.22.35.39
v2n1.nic.plus. 155349 A 161.232.17.39
v0n0.nic.plus. 155349 AAAA 2a01:8840:22:0:0:0:0:39
v0n1.nic.plus. 155349 AAAA 2a01:8840:23:0:0:0:0:39
v0n2.nic.plus. 170658 AAAA 2a01:8840:24:0:0:0:0:39
v0n3.nic.plus. 155349 AAAA 2a01:8840:fa:0:0:0:0:39
v2n0.nic.plus. 170658 AAAA 2a01:8840:25:0:0:0:0:39
v2n1.nic.plus. 155349 AAAA 2a01:8840:fb:0:0:0:0:39
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0