Apex domains cannot have CNAME records.
Question and response
Question
dig sentia.cloud. NS
Answer
sentia.cloud. 5 NS dns1.sentia.dk.
sentia.cloud. 5 NS dns3.sentia.dk.
sentia.cloud. 5 NS dns2.sentia.dk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0