Apex domains cannot have CNAME records.
Question and response
Question
dig empty.us.com. NS
Answer
empty.us.com. 3 NS dns100.ovh.net.
empty.us.com. 3 NS ns100.ovh.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0