Apex domains cannot have CNAME records.
Question and response
Question
dig UU.NET. NS
Answer
uu.net. 1 NS auth200.ns.uu.net.
uu.net. 1 NS auth00.ns.uu.net.
uu.net. 1 NS auth60.ns.uu.net.
uu.net. 1 NS auth210.ns.uu.net.
Authority
The response has no authority records.
Additional
auth00.ns.uu.net. 1 A 198.6.1.65
auth60.ns.uu.net. 1 A 198.6.1.181
auth200.ns.uu.net. 1 A 195.129.12.82
auth210.ns.uu.net. 1 A 195.129.12.74
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0