Preparation

• Position a rack in the center of the oven and heat the oven to 450°F.
• Line a large rimmed sheet pan with aluminum foil or parchment and mist with cooking spray. Toss the potatoes and onion together on the prepared pan.
• In a small bowl, whisk together 1/4 cup of the oil, 1 Tbs. of the mustard, the mashed garlic, and a big pinch each of salt and pepper. Reserve 2 Tbs. and drizzle the remaining mixture over the vegetables on the sheet pan, tossing to coat. Spread the vegetables evenly and roast until beginning to soften and color slightly, 10 to 15 minutes.
• Meanwhile, pat the pork tenderloins dry with a paper towel. In a small bowl, combine the remaining 1 Tbs. oil and mustard with the sugar, 1 tsp. salt, and 1/2 tsp. pepper; rub all over the pork. Sprinkle the chopped fresh herbs to coat on all sides.
• Toss the apple wedges with the reserved 2 Tbs. of dressing, then toss with the vegetables on the pan. Place the tenderloins on top of the vegetables, leaving some space between the two pieces of meat.
• Roast, flipping the meat once halfway through, until the vegetables are browned and tender and an instant-read thermometer inserted into the thickest part of the pork registers 145°F, 25 to 30 minutes total.
• Transfer the pork to a cutting board and let rest, loosely covered with aluminum foil, for 10 minutes. Meanwhile, toss the vegetables with the vinegar.
• Slice the pork, sprinkle with sea salt, and serve with the vegetables.