Apex domains cannot have CNAME records.
Question and response
Question
dig cirt.cm. NS
Answer
cirt.cm. 5 NS ns3.cirt.cm.
cirt.cm. 5 NS ns1.cirt.cm.
Authority
The response has no authority records.
Additional
ns1.cirt.cm. 5 A 154.126.128.20
ns3.cirt.cm. 5 A 197.159.0.70
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0