Apex domains cannot have CNAME records.
Question and response
Question
dig mcp-gmbh.com. NS
Answer
mcp-gmbh.com. 5 NS ns-1620.awsdns-10.co.uk.
mcp-gmbh.com. 5 NS ns-732.awsdns-27.net.
mcp-gmbh.com. 5 NS ns-19.awsdns-02.com.
mcp-gmbh.com. 5 NS ns-1423.awsdns-49.org.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0