Apex domains cannot have CNAME records.
Question and response
Question
dig cdw.com. NS
Answer
cdw.com. 3 NS a11-65.akam.net.
cdw.com. 3 NS a13-66.akam.net.
cdw.com. 3 NS a1-183.akam.net.
cdw.com. 3 NS a22-65.akam.net.
cdw.com. 3 NS a2-66.akam.net.
cdw.com. 3 NS a12-67.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0