Apex domains cannot have CNAME records.
Question and response
Question
dig mdcs.at. NS
Answer
mdcs.at. 2 NS ns0048.secondary.cloudflare.com.
mdcs.at. 2 NS ns0175.secondary.cloudflare.com.
Authority
The response has no authority records.
Additional
ns0048.secondary.cloudflare.com. 4 A 162.159.32.49
ns0175.secondary.cloudflare.com. 4 A 162.159.33.50
ns0048.secondary.cloudflare.com. 4 AAAA 2606:4700:51:0:0:0:a29f:2031
ns0175.secondary.cloudflare.com. 4 AAAA 2606:4700:59:0:0:0:a29f:2132
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0