Apex domains cannot have CNAME records.
Question and response
Question
dig truezuid.nl. NS
Answer
truezuid.nl. 4 NS nsauth3.pinkzuid.nl.
truezuid.nl. 4 NS nsauth2.pinkzuid.nl.
truezuid.nl. 4 NS nsauth1.pinkzuid.nl.
Authority
The response has no authority records.
Additional
nsauth1.pinkzuid.nl. 4 A 91.208.229.6
nsauth2.pinkzuid.nl. 4 A 91.208.229.72
nsauth3.pinkzuid.nl. 4 A 87.233.219.178
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0