Place a rack in the center of your oven and preheat the oven to 375 degrees F.

Place the sun-dried tomatoes in a bowl and cover with hot water to rehydrate. Let rest 5 minutes.

While the tomatoes rehydrate, dice the onion. Then, drain the sun-dried, pat dry, and finely chop.

In a large (12-inch), oven-safe skillet, heat 2 tablespoons of the oil over medium-high heat. Add the onions, ½ teaspoon sage, rosemary, ½ teaspoon salt, and ¼ teaspoon black pepper. Sauté until the onions soften and begin to brown, about 5 minutes.

Add the spinach a few handfuls at a time, stirring so that it wilts down.

Once the spinach has wilted, stir in the garlic and sun-dried tomatoes. Cook until fragrant being careful that the garlic doesn’t burn, about 1 minute.

Turn off the heat. Stir in the Parmesan. Transfer the filling to a plate and let cool slightly. With a paper towel, carefully wipe out the skillet and keep it handy.

Cut away and discard the silver skin from the pork tenderloin. Butterfly the pork by cutting a slit down the tenderloin lengthwise, but don't quite slice it all the way through. The 2 sides should remain attached.

Open the pork tenderloin flat like a book and cover it with a large sheet of plastic wrap. Lightly pound it to an even, ½-inch thickness.

Cover the tenderloin with a single layer of overlapping prosciutto slices.

Spoon the spinach filling evenly on the cut side of the pork.

Starting with a long edge, roll it up jelly-roll style. Secure the seam with toothpicks (you’ll need 6-7), inserting the toothpicks parallel to the meat so that they lay flat. Season the outside with the remaining 1/2 teaspoon salt and 1/4 teaspoon pepper.

In the same skillet, heat the remaining 1 tablespoon oil over medium heat until oil is hot but not smoking. Swirl the pan to coat, then place tenderloin in the skillet, toothpick-side up. Transfer to oven and roast for 15 minutes.

Remove the skillet from the oven, flip pork over and continue roasting until meat reaches 135 to 140 degrees on an instant read thermometer at the thickest part of the meat, about 10 to 12 minutes longer. Transfer to a cutting board, cover, and let rest for 10 minutes (the carry-over cooking will bring the meat up to 145 degrees F).

Make the sauce: return the same skillet to medium heat, then stir in the white wine and remaining ½ teaspoon sage, scraping up the browned bits on the bottom of the pan. Let the wine reduce by half, then stir in the broth and lemon juice.

Increase the heat to medium-high heat and cook until slightly thickened, about 5 minutes more. Stir in the butter. Taste and add additional salt and pepper as desired.

To serve, cut the pork into rings and top with a spoonful of the sauce and a squeeze of additional lemon juice and a sprinkle of parsley if desired. Enjoy hot.