Step 1

Heat the oven to 475°F with a rack in the upper-middle position. Mist a rimmed baking sheet with cooking spray. Place the squash and onions on the baking sheet, then drizzle with 2 tablespoons oil and sprinkle with ½ teaspoon each salt and pepper; toss, then distribute in an even layer. Roast for 20 minutes. Meanwhile, in a small bowl, stir together the caraway, paprika, sugar and ½ teaspoon each salt and pepper. Coat each tenderloin with 1 tablespoon oil, then sprinkle both on all sides with the spice mixture, pressing so the seasonings adhere.

Step 2

Remove the baking sheet from the oven. Using a wide metal spatula, flip the vegetables and push them to the perimeter of the baking sheet. Place the tenderloins in the center, evenly spacing them. Return to the oven and roast until the centers of the tenderloins reach 135°F and a skewer inserted into the squash meets no resistance, 18 to 20 minutes.

Step 3

Transfer the tenderloins to a cutting board; transfer the squash and onions to a platter. Add the cider, vinegar and mustard to the baking sheet, then scrape up any browned bits. Add the butter and chives; whisk until the butter is melted. Taste and season with salt and pepper.

Step 4

Slice the tenderloins and transfer them to the platter. Pour the sauce and any accumulated juices on the cutting board over the pork and vegetables.