Apex domains cannot have CNAME records.
Question and response
Question
dig aspentechlabs.com. NS
Answer
aspentechlabs.com. 4 NS ns-1309.awsdns-35.org.
aspentechlabs.com. 4 NS ns-719.awsdns-25.net.
aspentechlabs.com. 4 NS ns-156.awsdns-19.com.
aspentechlabs.com. 4 NS ns-1597.awsdns-07.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0