Apex domains cannot have CNAME records.
Question and response
Question
dig wolterskluwer.ivcert.net. NS
Answer
wolterskluwer.ivcert.net. 1 NS ns-290.awsdns-36.com.
wolterskluwer.ivcert.net. 1 NS ns-1566.awsdns-03.co.uk.
wolterskluwer.ivcert.net. 1 NS ns-1166.awsdns-17.org.
wolterskluwer.ivcert.net. 1 NS ns-665.awsdns-19.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0