2. Place the butternut squash, cut side down, on a microwave-safe plate. Microwave on high till the squash is tender, about 12 to 15 minutes.
3. Meanwhile, heat a large cast-iron skillet over high heat. Season the pork with salt and pepper to taste. When the pan is hot, coat it with the cooking spray. Add the pork to the pan and sear on all sides, about 3 minutes per side. Transfer the pork to a baking sheet and continue cooking in the oven till done, about 10 to 15 minutes, or until the internal temperature reaches 155°F Remove the baking sheet from the oven, and tent the meat with foil to keep it warm. Let the meat rest for at least 10 minutes before slicing.
4. In the same pan over medium-low heat, add the applesauce, scraping up any flavorful bits with a wooden spoon. Add the mustard, apple cider, 2 teaspoons agave, and tarragon. Stir continuously until the sauce thickens. Season with salt and pepper to taste.
5. With a spoon, scoop the flesh of the squash into a medium bowl. Mash the squash with a fork, and add the nutmeg grates and remaining agave. Stir till combined. Season with salt and pepper to taste.
6. With a sharp knife, thinly slice the pork. Serve the pork with the reduced sauce and the butternut squash. Sprinkle the walnuts on top of the pork.