Pork: Put an oven rack in the center of the oven. Preheat the oven to 400 degrees F.
Rub 1 tablespoon of the oil over the pork and season with salt and pepper, to taste. In a large skillet or Dutch oven, heat the remaining 2 tablespoons of oil over high heat. Add the pork and brown it on all sides, about 8 minutes. Transfer the pork to a 13 by 9 by 2-inch glass baking dish and roast it until an instant-read thermometer inserted into the thickest part of the pork registers 165 degrees F, about 25 to 30 minutes. Allow the pork to rest for 10 minutes on a cutting board.
Sauce: In the same skillet used for the pork, heat the oil over medium-high heat. Add the onion, peppers and garlic and season with salt and pepper, to taste. Cook, stirring frequently until softened, about 8 to 10 minutes. Add the wine and cook for 2 minutes, scraping up the brown bits that cling to the bottom of the pan with a wooden spoon. Stir in the paprika, tomato puree and the bay leaf. Bring the mixture to a boil. Reduce the heat to a simmer and cook until the sauce thickens, about 25 to 30 minutes. Remove the bay leaf and transfer the mixture to a food processor or blender. Blend until smooth. Season with 2 tablespoons salt and pepper, to taste.
Slice the pork thinly and arrange on a platter. Spoon the sauce on top, garnish with chopped parsley and serve.