Apex domains cannot have CNAME records.
Question and response
Question
dig hireserve.nl. NS
Answer
hireserve.nl. 5 NS ns5.firstfind.net.
hireserve.nl. 5 NS ns4.firstfind.nl.
hireserve.nl. 5 NS ns3.firstfind.nl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0