Combine turbinado, soy sauce and garlic in a medium bowl & stir.

Wash & dry the backstrap.  Slice venison into medallions & place into bowl with marinade.  Be sure all the meat is coated.  Cover and let marinade 1-2 hours.

Heat lard or bacon grease in a large cast-iron skillet.  Fry the venison over medium high heat until medium-rare (about 2 minutes per side).  Move venison to platter to rest.

Slice 1 onion & add to skillet.  Cook until soft.  Add 2 cups broth to skillet.  Cook until reduced by half (about 5 minutes).   Add butter to sauce.

Serve the sauce over venison medallions.