Apex domains cannot have CNAME records.
Question and response
Question
dig uunet.be. NS
Answer
uunet.be. 1 NS auth50.ns.be.uu.net.
uunet.be. 1 NS auth00.ns.be.uu.net.
Authority
The response has no authority records.
Additional
auth00.ns.be.uu.net. 4 AAAA 2001:600:1c0:e000:0:0:35:4
auth50.ns.be.uu.net. 4 AAAA 2001:600:1c0:e001:0:0:35:4
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0