Apex domains cannot have CNAME records.
Question and response
Question
dig mtmsys.us. NS
Answer
mtmsys.us. 4 NS ns02.momentumtelecom.com.
mtmsys.us. 4 NS ns04.momentumtelecom.com.
mtmsys.us. 4 NS ns01.momentumtelecom.com.
Authority
The response has no authority records.
Additional
ns01.momentumtelecom.com. 4 A 209.55.18.40
ns02.momentumtelecom.com. 4 A 208.67.15.68
ns04.momentumtelecom.com. 4 A 35.173.255.124
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0