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