Apex domains cannot have CNAME records.
Question and response
Question
dig ARMY.MIL. NS
Answer
ARMY.MIL. 4 NS ns03.ARMY.MIL.
ARMY.MIL. 4 NS ns01.ARMY.MIL.
ARMY.MIL. 4 NS ns02.ARMY.MIL.
Authority
The response has no authority records.
Additional
NS01.ARMY.MIL. 4 A 140.153.43.44
NS02.ARMY.MIL. 4 A 192.82.113.7
NS03.ARMY.MIL. 4 A 130.114.200.6
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0