Apex domains cannot have CNAME records.
Question and response
Question
dig materna-com.de. NS
Answer
materna-com.de. 5 NS ns3.domaindiscount24.net.
materna-com.de. 5 NS ns2.domaindiscount24.net.
materna-com.de. 5 NS ns1.domaindiscount24.net.
materna-com.de. 5 NS mcn-ext-dns-2.materna.de.
Authority
The response has no authority records.
Additional
ns1.domaindiscount24.net. 5 A 193.227.117.34
ns2.domaindiscount24.net. 5 A 194.50.187.34
ns3.domaindiscount24.net. 5 A 194.0.182.34
mcn-ext-dns-2.materna.de. 5 A 3.123.207.100
ns1.domaindiscount24.net. 5 AAAA 2a04:2b00:14cc:0:0:0:0:34
ns2.domaindiscount24.net. 5 AAAA 2a04:2b00:14dd:0:0:0:0:34
ns3.domaindiscount24.net. 5 AAAA 2a04:2b00:14ee:0:0:0:0:34
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0