Apex domains cannot have CNAME records.
Question and response
Question
dig cdn.webflow.com. NS
Answer
cdn.webflow.com. 5 NS journey.ns.cloudflare.com.
cdn.webflow.com. 5 NS lamar.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0