Apex domains cannot have CNAME records.
Question and response
Question
dig trido.nl. NS
Answer
trido.nl. 1 NS dnsauth1.tnoc.nl.
trido.nl. 1 NS dnsauth2.tnoc.nl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0