Apex domains cannot have CNAME records.
Question and response
Question
dig megamail.nl. NS
Answer
megamail.nl. 5 NS ns2.hix.nl.
megamail.nl. 5 NS ns1.hix.nl.
megamail.nl. 5 NS ns-3.eu.
Authority
The response has no authority records.
Additional
ns1.hix.nl. 2 A 83.137.192.101
ns2.hix.nl. 2 A 31.3.110.75
ns-3.eu. 2 A 85.10.135.155
ns1.hix.nl. 2 AAAA 2a00:a0c0:3:0:0:0:1:2
ns-3.eu. 2 AAAA 2a01:7c8:d007:462:0:0:0:155
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0