Apex domains cannot have CNAME records.
Question and response
Question
dig madisonmk.com. NS
Answer
madisonmk.com. 5 NS ns-516.awsdns-00.net.
madisonmk.com. 5 NS ns-1444.awsdns-52.org.
madisonmk.com. 5 NS ns-1634.awsdns-12.co.uk.
madisonmk.com. 5 NS ns-261.awsdns-32.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0