Apex domains cannot have CNAME records.
Question and response
Question
dig farsightsecurity.com. NS
Answer
farsightsecurity.com. 1 NS ns5.dnsmadeeasy.com.
farsightsecurity.com. 1 NS ns6.dnsmadeeasy.com.
farsightsecurity.com. 1 NS ns7.dnsmadeeasy.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0