2 teaspoons kosher salt
2 teaspoons finely chopped fresh rosemary leaves
1/4 teaspoon freshly ground black pepper
1 medium butternut squash (about 2 1/2 pounds)
3 tablespoons unsalted butter
1 medium yellow onion
2 ripe, but firm pears (about one pound)
Heat the oven to 475°F and arrange a rack in the middle. Place a baking sheet in the oven as it heats. Mix the salt, rosemary, and black pepper in a small bowl; set aside.
Peel the skin from the squash with a vegetable peeler. Trim the top and bottom. Cut the neck from the bulb of the squash. Halve each piece lengthwise and scrape out the seeds. Cut the squash into 3/4-inch cubes and place in a large bowl.
Melt 1 tablespoon of the butter and add it to the squash. Add half of the reserved salt mixture and toss to combine. Remove the hot baking sheet from the oven and spread the squash into an even layer on it. Roast until the squash is golden brown on the bottom, about 25 minutes. Using a flat spatula, stir and continue roasting until knife tender, about 10 minutes more. Meanwhile, prepare the onion and pears.
Cut the onion into medium dice; set aside. Peel, core, and cut the pears into large dice; set aside. Melt the remaining 2 tablespoons of butter in a large frying pan over medium heat. Add the onion and cook, stirring occasionally, until softened, about 10 minutes. Add the pears and remaining half of the salt mixture and cook, stirring occasionally, until the pears are knife tender, about 5 to 6 minutes more. Remove the pan from the heat. When the squash is ready, add it to the pan with the onions and pears, toss to combine, and serve.