How to Make It
In a bowl, soak the chiles in hot water until softened, about 20 minutes. In another bowl, soak the sun-dried tomatoes in hot water until softened, about 15 minutes. Drain the chiles and tomatoes; coarsely chop the chiles.
Heat the oil in a skillet. Add the onion, chiles and sun-dried tomatoes and cook over moderately low heat until softened, about 6 minutes. Transfer to a blender and add the orange juice, lemon juice, tomato paste, orange zest, tarragon, oregano and 2 tablespoons of kosher salt. Puree until smooth.
Preheat the oven to 450°. Roast the pork in a roasting pan for about 15 minutes, or until starting to brown. Spread 6 tablespoons of the chile paste on the pork. Lower the oven temperature to 375° and roast for 10 minutes. Spread 2 more tablespoons of the chile paste on the pork and roast for about 30 minutes more, or until an instant-read thermometer inserted in the meat reads 145°. Cover with foil and let rest for 5 minutes. Season the meat with salt and pepper.
In a nonstick skillet, cook the pear slices over moderately high heat, without stirring, until tender and golden, about 4 minutes. Arrange the watercress and pears on a platter. Slice the pork 1/4 inch thick and arrange on top.