Pork and prunes are a classic pairing in northern Italian cooking, and this twist delivers protein, polyphenols, and vitamins and minerals. If you don’t have Marsala wine on hand, try subbing in some red, or even rosé.
Preheat oven to 375°F. Heat 2 tablespoons oil in a large ovenproof skillet over medium-high. Sprinkle pork evenly with 3/4 teaspoon salt and pepper. Add pork to skillet; sear, turning occasionally, until browned on all sides, 8 to 10 minutes total.
Transfer skillet to oven. Bake until a thermometer inserted in thickest portion of pork registers 145°F, 20 to 25 minutes. Transfer pork to a cutting board; let rest 10 minutes.
While pork cooks and rests, microwave prunes and Marsala together in a small microwavable bowl on High until Marsala comes to a boil, about 90 seconds. Let stand 10 minutes. Drain prunes (discarding Marsala).
In another skillet, add 1 tablespoon oil. Add squash noodles, and cook over medium, gently stirring often, until crisp-tender, about 5 minutes. Remove from heat.
Toss together arugula, squash noodles, prunes, orange zest, orange juice, chopped oranges, remaining 2 tablespoons oil, and remaining 1/2 teaspoon salt in a large bowl. Cut pork crosswise into slices; divide evenly among 4 plates. Serve with arugula salad.