Apex domains cannot have CNAME records.
Question and response
Question
dig telekom.de. NS
Answer
telekom.de. 5 NS pns.dtag.de.
telekom.de. 5 NS ns1.telekom.net.
telekom.de. 5 NS dns2.telekom.de.
telekom.de. 5 NS dns1.telekom.de.
Authority
The response has no authority records.
Additional
dns1.telekom.de. 5 A 194.25.225.19
dns2.telekom.de. 5 A 194.25.225.3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0