Apex domains cannot have CNAME records.
Question and response
Question
dig wolterskluwer.com. NS
Answer
wolterskluwer.com. 5 NS ns-405.awsdns-50.com.
wolterskluwer.com. 5 NS ns-1088.awsdns-08.org.
wolterskluwer.com. 5 NS ns-537.awsdns-03.net.
wolterskluwer.com. 5 NS ns-1985.awsdns-56.co.uk.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0