Apex domains cannot have CNAME records.
Question and response
Question
dig chartermi.net. NS
Answer
chartermi.net. 1 NS ns1.charter.com.
chartermi.net. 1 NS ns4.charter.com.
chartermi.net. 1 NS ns3.charter.com.
chartermi.net. 1 NS ns2.charter.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0