Apex domains cannot have CNAME records.
Question and response
Question
dig coastal.com. NS
Answer
coastal.com. 5 NS a22-64.akam.net.
coastal.com. 5 NS a3-65.akam.net.
coastal.com. 5 NS a7-66.akam.net.
coastal.com. 5 NS a1-51.akam.net.
coastal.com. 5 NS a2-67.akam.net.
coastal.com. 5 NS a10-66.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0