Apex domains cannot have CNAME records.
Question and response
Question
dig as. NS
Answer
as. 5 NS ns5.asnic.us.
as. 5 NS ns1.asnic.biz.
as. 5 NS ns3.asnic.org.
as. 5 NS ns2.asnic.info.
as. 5 NS ns4.asnic.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0