Hi Ola,
man thats a tough customer to fix, TT500 frames do similar ugly things when the engine mounts get loose and flog out.
So you may have to address the engine mounting bolt holes in the frame and brace the area with a couple of gussets behind to bridge the fracture. To stop it happening again. Still relatively rare bike and worth the effort of learning to braze.
On second thought you had better sell it cheap to me.