Pat dry the pork and season it with 1 ½ salt. Let it sit while you make the marinade.

To make the marinade, combine the 1 cup wine, ¼ olive oil, ¼ vinegar, 1 cup prunes, 1 cup olives, ⅓ cup capers and brine, 4 bay leaves, 4 cloves garlic, ⅓ cup brown sugar, 2 tablespoon oregano, in a large bowl. Add the pork to the marinade. (You can also place the pork and marinade in a large resealable plastic storage bag and squeeze out the air to make sure the pork is fully covered with the marinade.) Refrigerate for 2 hours or overnight, turning occasionally to be sure the marinade is getting into all sides of the pork.

Preheat oven to 325°. Remove pork from marinade and pat dry; reserve marinade. Heat remaining 2 Tbsp. olive oil in a 12" skillet over medium-high. Cook pork, undisturbed for a few minutes, until it is golden brown. Then repeat on the other side.

Remove the pan from heat and let the pan cool 1 minute and then pour reserved marinade around pork. Transfer pan to the center of the oven and bake, basting pork once with its sauce halfway through, until an instant-read thermometer inserted into the thickest part of tenderloin registers 145°, about 15–20 minutes, depending on thickness.

Transfer the pork to a cutting board and allow to rest for 10 minutes.

Discard the bay leaves. Return pan with the marinade to medium-high heat. Add 1 tablespoon butter and cook, stirring pan occasionally, until slightly reduced, 5-8 minutes.

Slice tenderloin in ½" slices and transfer back to a pan with the sauce and serve.