Apex domains cannot have CNAME records.
Question and response
Question
dig pod029.cloudkey.pt. NS
Answer
pod029.cloudkey.pt. 5 NS ns2.eventkey.pt.
pod029.cloudkey.pt. 5 NS ns1.eventkey.pt.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0