Apex domains cannot have CNAME records.
Question and response
Question
dig centex.net. NS
Answer
centex.net. 5 NS ns1.centex.net.
centex.net. 5 NS ns2.centex.net.
Authority
The response has no authority records.
Additional
ns1.centex.net. 5 A 74.84.8.21
ns2.centex.net. 5 A 74.84.8.22
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0