Apex domains cannot have CNAME records.
Question and response
Question
dig sertoma.org. NS
Answer
sertoma.org. 5 NS ns49.worldnic.com.
sertoma.org. 5 NS ns50.worldnic.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0