Apex domains cannot have CNAME records.
Question and response
Question
dig dentalemergencyatlanta.com. NS
Answer
dentalemergencyatlanta.com. 4 NS ns27.domaincontrol.com.
dentalemergencyatlanta.com. 4 NS ns28.domaincontrol.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0