Apex domains cannot have CNAME records.
Question and response
Question
dig xlink.net. NS
Answer
xlink.net. 5 NS ulm.nic.xlink.net.
xlink.net. 5 NS chemnitz.nic.xlink.net.
Authority
The response has no authority records.
Additional
ulm.nic.xlink.net. 5 A 193.141.3.6
chemnitz.nic.xlink.net. 5 A 194.45.97.99
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0