A one-pan dish that really brings the flavor, this simple meal will easily feed your whole family.
Preheat oven to 475 degrees. On a rimmed baking sheet, toss sweet potato, parsnips, and ginger with oil and spread in an even layer. Mix together brown sugar and cayenne and rub all over pork; add to sheet. Season pork and vegetables with salt and roast until an instant-read thermometer inserted in center of pork reads 145 degrees, 20 to 22 minutes. Let pork rest 10 minutes before serving.
Toss vegetables with watercress, drizzle with olive oil, and season. Thinly slice pork and serve with any accumulated juices from sheet, the salad, and lime wedges.
Beyond the Peel To remove ginger skin easily, scrape with the edge of a spoon.