Apex domains cannot have CNAME records.
Question and response
Question
dig cust.t4tel.com. NS
Answer
cust.t4tel.com. 5 NS ns.cust.t4tel.com.
Authority
The response has no authority records.
Additional
ns.cust.t4tel.com. 5 A 34.72.239.93
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0