Apex domains cannot have CNAME records.
Question and response
Question
dig irt-hosting.net. NS
Answer
irt-hosting.net. 5 NS ns2.dns.nms.gtt.net.
irt-hosting.net. 5 NS ns1.dns.nms.gtt.net.
irt-hosting.net. 5 NS ns3.dns.nms.gtt.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0