Apex domains cannot have CNAME records.
Question and response
Question
dig circle.so. NS
Answer
circle.so. 4 NS james.ns.cloudflare.com.
circle.so. 4 NS tori.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0