Apex domains cannot have CNAME records.
Question and response
Question
dig openedu.nl. NS
Answer
openedu.nl. 3 NS ns1.gateworks.nl.
openedu.nl. 3 NS ns2.gateworks.nl.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0