Apex domains cannot have CNAME records.
Question and response
Question
dig nextgenfibre.ie. NS
Answer
nextgenfibre.ie. 5 NS ns1.blacknightdns.com.
nextgenfibre.ie. 5 NS ns4.blacknightdns.com.
nextgenfibre.ie. 5 NS ns3.blacknightdns.com.
nextgenfibre.ie. 5 NS ns2.blacknightdns.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0