Apex domains cannot have CNAME records.
Question and response
Question
dig esatclear.ie. NS
Answer
esatclear.ie. 5 NS pixie.esatclear.ie.
esatclear.ie. 5 NS ns.esatclear.ie.
esatclear.ie. 5 NS sec01.ns.esat.net.
Authority
The response has no authority records.
Additional
ns.esatclear.ie. 5 A 194.145.128.1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0