Apex domains cannot have CNAME records.
Question and response
Question
dig service-now.com. NS
Answer
service-now.com. 5 NS eur6.akam.net.
service-now.com. 5 NS use1.akam.net.
service-now.com. 5 NS aus1.akam.net.
service-now.com. 5 NS edns140.ultradns.org.
service-now.com. 5 NS edns140.ultradns.net.
service-now.com. 5 NS edns140.ultradns.com.
service-now.com. 5 NS edns140.ultradns.biz.
service-now.com. 5 NS usw1.akam.net.
service-now.com. 5 NS use3.akam.net.
service-now.com. 5 NS usc4.akam.net.
service-now.com. 5 NS ns1-234.akam.net.
service-now.com. 5 NS ns1-98.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0