I loved the flavors in this dish - it is all very simple. Basic ingredients - spinach, onions, pork, cheese (I used Swiss instead of cheddar), and tomatoes. I also hate wasting any of the cooked bits of stuff on the bottom of the pan, so I made a pan sauce to go with this - just threw in some garlic, white wine, chicken stock, and butter. I've now tried to butterfly tenderloin twice in the last week, and I still stink at it. Mine wasn't all pretty and rolled up, but it still tasted great!
adapted from Jacques Pepin: More Fast Food My Way
4 tablespoons good olive oil
1/2 cup chopped onion
1 package (7 ounces) prewashed baby spinach
3/4 teaspoon salt
3/4 teaspoon freshly ground black pepper
1 large pork tenderloin (about 1 1/4 pounds)
3/4 cup grated cheddar cheese
1 box grape tomatoes (about 1 1/2 pints)
1 Tbsp olive oil
1/2 cup white wine (or can sub chicken stock)
1/2 - 1 cup chicken stock
2-3 cloves garlic, minced
2 Tbsp butter
Heat 2 tablespoons of the olive oil in a large skillet over high heat. Add the onion and cook for 1 minute. Add the spinach, pushing it down into the skillet, and 1/4 teaspoon each of the salt and pepper. Cover and cook over medium heat for about 1 1/2 minutes, until the spinach is wilted. Remove the lid and cook, uncovered, until the liquid from the spinach has evaporated. Transfer to a plate and let cool.
Trim the tenderloin of any fat and silverskin. To butterfly the tenderloin for stuffing, lay it flat on the cutting board so one end is close to you and the other end is near the top of the board. Holding your knife so the blade is parallel to the board, cut through the long side of the tenderloin, stopping when you are about 1/2 inch from the other side. Turn the tenderloin so the uncut side is closest to you and make another parallel cut below the first one, again stopping about 1/2 inch before you reach the other side. Open up the butterflied tenderloin and pound it a little to extend it to about 12 inches long by 7 inches wide.
Preheat the oven to 350 degrees. Arrange half the spinach mixture down the center of the butterflied tenderloin and top with the cheese. Add the rest of the spinach, fold in the sides, and roll the tenderloin back and forth to evenly distribute and encase the filling. Wrap 2 strips of aluminum foil, each 1 to 2 inches wide, around the tenderloin to secure the stuffing inside.
Heat the remaining 2 tablespoons oil in a large ovenproof nonstick skillet. Sprinkle the outside of the tenderloin with 1/4 teaspoon each of the salt and pepper. Place the tenderloin carefully in the skillet and brown it, turning occasionally, for about 5 minutes. Carefully remove the foil strips from the tenderloin and bake in the oven for 10 minutes, when it will be slightly pink in the center. Transfer the tenderloin to a plate, cover, and keep warm in the oven while you prepare the tomatoes & pan sauce (the pork will continue to cook as it sits).
In the same pan you roasted the pork in, heat 1 Tbsp olive oil over medium heat. Add garlic and saute for a minute or so. Add in the wine, stock, and butter (turn off the gas burner while adding wine). Let it simmer to desired consistency.
Add the tomatoes and the remaining 1/4 teaspoon each salt and pepper to the skillet and sauté over high heat for 1 1/2 to 2 minutes, until just softened.