Apex domains cannot have CNAME records.
Question and response
Question
dig static.bellmts.net. NS
Answer
static.bellmts.net. 5 NS dns2.mts.net.
static.bellmts.net. 5 NS dns1.mts.net.
Authority
The response has no authority records.
Additional
dns1.mts.net. 5 A 205.200.16.65
dns2.mts.net. 5 A 205.200.16.69
dns1.mts.net. 5 AAAA 2607:ca00:8100:a:0:0:0:f011
dns2.mts.net. 5 AAAA 2607:ca00:8100:a:0:0:0:e011
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0