Apex domains cannot have CNAME records.
Question and response
Question
dig 3uu.net. NS
Answer
3uu.net. 5 NS rc79.3uu.net.
3uu.net. 5 NS rc78.3uu.net.
Authority
The response has no authority records.
Additional
rc78.3uu.net. 5 A 85.10.248.116
rc79.3uu.net. 5 A 85.10.248.117
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0