Apex domains cannot have CNAME records.
Question and response
Question
dig premiumantispam.nl. NS
Answer
premiumantispam.nl. 5 NS ns1.dn-s.nl.
premiumantispam.nl. 5 NS ns4.dn-s.nl.
premiumantispam.nl. 5 NS ns3.dn-s.nl.
premiumantispam.nl. 5 NS ns2.dn-s.nl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0