Apex domains cannot have CNAME records.
Question and response
Question
dig previder.nl. NS
Answer
previder.nl. 3 NS nsauth3.introweb.net.
previder.nl. 3 NS nsauth2.introweb.nl.
previder.nl. 3 NS nsauth1.introweb.nl.
Authority
The response has no authority records.
Additional
nsauth3.introweb.net. 1 A 62.165.127.221
nsauth3.introweb.net. 1 AAAA 2001:1690:1:c:0:0:0:a
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0