Apex domains cannot have CNAME records.
Question and response
Question
dig mxmfb.com. NS
Answer
mxmfb.com. 5 NS ns-1128.awsdns-13.org.
mxmfb.com. 5 NS ns-823.awsdns-38.net.
mxmfb.com. 5 NS ns-129.awsdns-16.com.
mxmfb.com. 5 NS ns-2035.awsdns-62.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0