Apex domains cannot have CNAME records.
Question and response
Question
dig turktelekommobile.de. NS
Answer
turktelekommobile.de. 5 NS finley.ns.cloudflare.com.
turktelekommobile.de. 5 NS edna.ns.cloudflare.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0