Apex domains cannot have CNAME records.
Question and response
Question
dig citibob.com. NS
Answer
citibob.com. 5 NS ns1.citibob.com.
citibob.com. 5 NS ns2.citibob.com.
Authority
The response has no authority records.
Additional
ns1.citibob.com. 5 A 139.99.68.138
ns2.citibob.com. 5 A 51.79.226.239
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0