Apex domains cannot have CNAME records.
Question and response
Question
dig mncable.net. NS
Answer
mncable.net. 2 NS auth1.america.net.
mncable.net. 2 NS auth2.america.net.
mncable.net. 2 NS auth5.america.net.
Authority
The response has no authority records.
Additional
auth1.america.net. 2 A 69.60.160.34
auth2.america.net. 2 A 69.60.160.35
auth5.america.net. 2 A 173.255.196.6
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0