Apex domains cannot have CNAME records.
Question and response
Question
dig ns.ie. NS
Answer
ns.ie. 5 NS i.ns.ie.
ns.ie. 5 NS a.ns.ie.
ns.ie. 5 NS c.ns.ie.
ns.ie. 5 NS e.ns.ie.
Authority
The response has no authority records.
Additional
a.ns.ie. 150422 A 77.72.72.40
a.ns.ie. 150422 AAAA 2a01:4b0:0:0:0:0:0:40
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0