Apex domains cannot have CNAME records.
Question and response
Question
dig dfn.nl. NS
Answer
dfn.nl. 4 NS ns2.dfn.nl.
dfn.nl. 4 NS ns1.dfn.nl.
Authority
The response has no authority records.
Additional
ns1.dfn.nl. 4 A 212.115.192.111
ns2.dfn.nl. 4 A 62.45.45.111
ns1.dfn.nl. 4 AAAA 2a02:f68:0:cf4:0:0:0:111
ns2.dfn.nl. 4 AAAA 2001:4c3a:100:b:0:0:0:111
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0