Apex domains cannot have CNAME records.
Question and response
Question
dig nic.onl. NS
Answer
nic.onl. 4 NS a0.nic.onl.
nic.onl. 4 NS a2.nic.onl.
nic.onl. 4 NS b0.nic.onl.
nic.onl. 4 NS c0.nic.onl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0