Apex domains cannot have CNAME records.
Question and response
Question
dig shortest-route.com. NS
Answer
shortest-route.com. 1 NS ns2.shortest-route.de.
shortest-route.com. 1 NS ns3.shortest-route.com.
shortest-route.com. 1 NS ns1.shortest-route.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0