I used a roast for this recipe but a loin will work just as well. Leave the fat on for a nice crisp presentation. I could not find my injector today so I just stabbed the roast in about 10 spots with a steak knife. Still soak it even if you inject. Choose a tall bowl that is not much bigger than your roast in order to soak the entire roast at once. Combine the white cranberry juice (I am sure red would do fine) and the Cherry Balsamic Vinegar and marinade roast all day. I started at 9am and cooked at 5pm. You should marinade a min. of 6 hours.
Remove the roast after it has soaked. Save the marinade for a side dish flavoring as I often do if you want.(See Homemade Rice-a-Roni) Place fat side up in a glass baking dish and combine spices and rub all over. Use a little extra cherry balsamic vinegar and a sprinkle of tarragon on top for prettiness.
Bake at 350 for about 2 hours and juices run clear. Adjust cooking time to size of roast. 40-45 mins a pound should do depending on how rare you like it. Mine is just a little pink in the center. Only cook rare with a good cut of meat like a tenderloin.