Apex domains cannot have CNAME records.
Question and response
Question
dig state.gov. NS
Answer
state.gov. 5 NS a3-66.akam.net.
state.gov. 5 NS a9-64.akam.net.
state.gov. 5 NS a1-63.akam.net.
state.gov. 5 NS a14-64.akam.net.
state.gov. 5 NS a26-65.akam.net.
state.gov. 5 NS a8-67.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0