In a small bowl, whisk together the mustards, soy sauce, and maple syrup. Place the pork in a large zip-top bag or shallow dish and thoroughly coat it with the mustard mixture. Cover and refrigerate for 1 to 3 hours.
While the pork is marinating, make the slaw: Place the cabbage, apple, and parsley in a large serving bowl and toss to combine. In a small bowl, whisk together the lemon juice, honey, vinegar, salt, and pepper and drizzle over the cabbage mixture. Cover and refrigerate until ready to serve.
Preheat the oven to 400°F. Heat the oil in a large ovenproof saute pan over medium-high heat. Add the pork and cook for 4 minutes on each side, until browned. Transfer the saute pan to the oven and roast for 15 minutes, until a meat thermometer inserted into the pork registers 165°F.
Transfer the pork to a cutting board and let it rest for 5 to 10 minutes before slicing, so the juices don’t escape.
Meanwhile, add the cider to the saute pan and heat over high, scraping up any browned bits in the pan, until the liquid reduces by half, about 5 minutes.
On each plate, place 3 slices of the pork and 1 ½ cups of the slaw. Drizzle about 1 tablespoon of the pan sauce over each serving of pork and serve.