Apex domains cannot have CNAME records.
Question and response
Question
dig gv.at. NS
Answer
gv.at. 5 NS ns4.wien.gv.at.
gv.at. 5 NS ns7.univie.ac.at.
gv.at. 5 NS ns12.govix.at.
gv.at. 5 NS dns4.statistik.gv.at.
gv.at. 5 NS ns3.wien.at.
gv.at. 5 NS ns8.univie.ac.at.
Authority
The response has no authority records.
Additional
ns4.wien.gv.at. 5 A 217.149.232.231
ns8.univie.ac.at. 5 A 81.91.161.104
dns4.statistik.gv.at. 5 A 193.170.163.166
ns4.wien.gv.at. 5 AAAA 2a00:1ba0:3:2502:0:0:0:231
ns8.univie.ac.at. 5 AAAA 2a02:568:20:0:0:0:0:8
dns4.statistik.gv.at. 5 AAAA 2001:628:2190:2520:0:0:0:166
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0