Apex domains cannot have CNAME records.
Question and response
Question
dig monkeybrains.NET. NS
Answer
monkeybrains.net. 5 NS ns1.monkeybrains.net.
monkeybrains.net. 5 NS ns2.monkeybrains.net.
monkeybrains.net. 5 NS ns3.monkeybrains.net.
Authority
The response has no authority records.
Additional
ns1.monkeybrains.net. 5 A 208.69.40.3
ns2.monkeybrains.net. 5 A 208.69.40.4
ns3.monkeybrains.net. 5 A 208.69.40.2
ns1.monkeybrains.net. 5 AAAA 2607:f598:0:1:0:0:0:2
ns2.monkeybrains.net. 5 AAAA 2607:f598:0:1:0:0:0:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0