Apex domains cannot have CNAME records.
Question and response
Question
dig frontbridge.com. NS
Answer
frontbridge.com. 2 NS ns1-gtm.glbdns.o365filtering.com.
frontbridge.com. 2 NS ns2-gtm.glbdns.o365filtering.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0