Preheat the oven to 400 degrees . In a gallon-size resealable plastic bag, combine the vinegar, olive oil and cumin. Add the pork and turn to coat; let marinate for 15 minutes.
Heat a large cast-iron skillet over medium heat. Season the pork with salt and cook, turning, until browned, about 10 minutes. Transfer the pan to the oven and roast until an instant-read thermometer inserted into the center registers 150 degrees , 15 to 20 minutes.
Meanwhile, in a medium bowl, combine the prunes and 1/4 cup hot water; let stand for 5 minutes. Stir in the oranges and season with salt and pepper.
Transfer the pork to a work surface and let rest for 10 minutes. Pour the orange-prune mixture into the skillet, scraping up any browned bits. Thinly slice the pork and season with salt. Top with the fruit mixture.