Apex domains cannot have CNAME records.
Question and response
Question
dig pixelpark.com. NS
Answer
pixelpark.com. 5 NS ns4.pixelpark.de.
pixelpark.com. 5 NS ns1.pixelpark.de.
pixelpark.com. 5 NS ns2.pixelpark.de.
pixelpark.com. 5 NS ns3.pixelpark.de.
Authority
The response has no authority records.
Additional
ns1.pixelpark.de. 3 A 93.188.110.60
ns2.pixelpark.de. 3 A 18.221.66.87
ns3.pixelpark.de. 3 A 35.156.14.171
ns4.pixelpark.de. 3 A 77.74.232.21
ns2.pixelpark.de. 3 AAAA 2600:1f16:2ee:d200:99c4:15e4:c039:8d3f
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0