Apex domains cannot have CNAME records.
Question and response
Question
dig cc.univie.ac.at. NS
Answer
cc.univie.ac.at. 5 NS ns4.univie.ac.at.
cc.univie.ac.at. 5 NS ns10.univie.ac.at.
cc.univie.ac.at. 5 NS ns3.univie.ac.at.
cc.univie.ac.at. 5 NS ns5.univie.ac.at.
cc.univie.ac.at. 5 NS ns8.univie.ac.at.
Authority
The response has no authority records.
Additional
ns3.univie.ac.at. 5 A 77.80.62.2
ns4.univie.ac.at. 5 A 131.130.249.82
ns5.univie.ac.at. 5 A 193.171.255.77
ns8.univie.ac.at. 5 A 81.91.161.104
ns10.univie.ac.at. 5 A 192.76.243.2
ns3.univie.ac.at. 5 AAAA 2001:62a:4:322:0:0:53:3
ns4.univie.ac.at. 5 AAAA 2001:62a:4:321:0:0:53:4
ns5.univie.ac.at. 5 AAAA 2001:628:453:4305:0:0:0:53
ns8.univie.ac.at. 5 AAAA 2a02:568:20:0:0:0:0:8
ns10.univie.ac.at. 5 AAAA 2001:67c:133c:0:0:0:0:2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0