Apex domains cannot have CNAME records.
Question and response
Question
dig bbtel.com. NS
Answer
bbtel.com. 5 NS ns1.bbtel.com.
bbtel.com. 5 NS ns2.blue.net.
bbtel.com. 5 NS ns1.blue.net.
Authority
The response has no authority records.
Additional
ns1.blue.net. 5 A 66.38.0.244
ns1.bbtel.com. 5 A 66.38.1.90
ns2.blue.net. 5 A 66.38.1.244
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0