Preparation time: 15 mins (plus 10 mins to rest)
Cooking time: 1 hr, 15 mins
1 teaspoon dried rosemary
1 teaspoon dried sage
1 teaspoon dried thyme plus a squeeze of lemon juice
1 teaspoon kosher salt
1/2 teaspoon ground black pepper
2-pound pork loin, fat trimmed, tied into a roast
2 teaspoons Dijon mustard
2 tablespoons vegetable oil
1 onion, halved and sliced into medium-thick wedges
2 tablespoons unsalted butter
2 teaspoons all-purpose flour, at room temperature
1/2 cup Marsala wine
1. Preheat the oven to 425 degrees F. Stir the rosemary, sage, thyme, salt, and pepper together in a small bowl. Place the pork roast on a cutting board and rub the mustard all over its surface, including the ends, Sprinkle and pat the herbs over the entire roast.
2. Heat the oil in an oven-safe skillet (cast iron is ideal). Brown the pork on all sides, about 15 minutes total. Remove the roast from the pan and set aside. Add the onion to the pan and toss to coat. Turn off the heat, nestle the roast in the middle of the pan, and place the roast in the oven for 15 minutes. Mash the butter and flour together to make a paste and set aside.
3. Reduce the oven temperature to 350 degrees F. and roast until the internal temperature of the pork reads about 150 degrees F., an additional 20 to 25 minutes. Remove the pan from the oven and place the pork on a cutting board, cover loosely with foil, and let it rest for 10 minutes.
4. Set the skillet on the stovetop over medium heat. Add the wine and stir to incorporate, then scrape in the butter-flour paste. Cook, stirring often for 2 minutes, to cook out the raw taste in the flour. Turn off the heat. Thinly slice the pork roast and serve with the sauce.