Apex domains cannot have CNAME records.
Question and response
Question
dig a2u2.com. NS
Answer
a2u2.com. 5 NS thor.a2u2.com.
a2u2.com. 5 NS odin.a2u2.com.
a2u2.com. 5 NS loki.a2u2.com.
Authority
The response has no authority records.
Additional
loki.a2u2.com. 5 A 66.185.25.212
odin.a2u2.com. 5 A 66.185.17.219
thor.a2u2.com. 5 A 162.253.134.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0