Apex domains cannot have CNAME records.
Question and response
Question
dig btbpo.net. NS
Answer
btbpo.net. 5 NS ns02.btsaas.net.
btbpo.net. 5 NS dns2.p08.nsone.net.
btbpo.net. 5 NS ns7.dnsmadeeasy.com.
btbpo.net. 5 NS ns6.dnsmadeeasy.com.
btbpo.net. 5 NS dns1.p08.nsone.net.
btbpo.net. 5 NS ns01.btsaas.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0