Apex domains cannot have CNAME records.
Question and response
Question
dig surveymonkey.com. NS
Answer
surveymonkey.com. 3 NS ns-588.awsdns-09.net.
surveymonkey.com. 3 NS ns-344.awsdns-43.com.
surveymonkey.com. 3 NS ns-1757.awsdns-27.co.uk.
surveymonkey.com. 3 NS ns-1380.awsdns-44.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0