Tektro Spyre C — is the rotor riveted to the hub?
Rotors are wear items and therefore must be removable. 

The Cube website does not specify what rotors are fitted, but I strongly suspect they are Shimano Center-lock which have a steel rotor riveted to an alloy ‘spider’.  They are fixed to the hub with a central lock ring. 

Changing the rotor will not improve braking performance, unless you are thinking of replacing it with a bigger one.