Apex domains cannot have CNAME records.
Question and response
Question
dig secondns.at. NS
Answer
secondns.at. 4 NS acglob.secondns.at.
secondns.at. 4 NS acglob.fifthns.com.
secondns.at. 4 NS acglob.fourthns.systems.
secondns.at. 4 NS acglob.firstns.cc.
secondns.at. 4 NS acglob.thirdns.de.
Authority
The response has no authority records.
Additional
acglob.fifthns.com. 4 A 185.81.208.1
acglob.thirdns.de. 4 A 213.227.160.1
acglob.fourthns.systems. 4 A 213.227.191.1
acglob.secondns.at. 4 A 188.172.248.1
acglob.fifthns.com. 4 AAAA 2a00:11c0:1010:0:0:0:0:1
acglob.thirdns.de. 4 AAAA 2605:380:aa1:0:0:0:0:1
acglob.fourthns.systems. 4 AAAA 2803:ad80:aa1:0:0:0:0:1
acglob.secondns.at. 4 AAAA 2a05:8900:aa1:0:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0