Apex domains cannot have CNAME records.
Question and response
Question
dig mailportal.cloud. NS
Answer
mailportal.cloud. 5 NS ns2.ennit.net.
mailportal.cloud. 5 NS ns1.ennit.net.
Authority
The response has no authority records.
Additional
ns1.ennit.net. 5 A 213.178.66.161
ns2.ennit.net. 5 A 82.97.146.5
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0