Apex domains cannot have CNAME records.
Question and response
Question
dig exactsoftware.com. NS
Answer
exactsoftware.com. 2 NS ns-2033.awsdns-62.co.uk.
exactsoftware.com. 2 NS ns-1149.awsdns-15.org.
exactsoftware.com. 2 NS ns-135.awsdns-16.com.
exactsoftware.com. 2 NS ns-794.awsdns-35.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0