Whisk together the honey, 2 tablespoons ancho, the mustard and chile de arbol in a small bowl until smooth then season with salt and pepper. Set aside. (If you can make this glaze at least 30 minutes before using, it will be more flavorful.)
Remove the pork from the refrigerator 30 minutes before cooking. Season the pork on both sides with salt, pepper and ancho powder. Heat a few tablespoons of oil in a large ovenproof skillet over high heat until it shimmers. Add the pork and cook on all sides until golden brown and a crust has formed, about 12 minutes total. Brush both sides with some of the glaze.
Transfer the skillet to the oven and roast until an instant-read thermometer inserted into the center registers 140 degrees F, about 12 minutes.
Brush the top with the glaze several times while roasting. Remove to a cutting board and brush the top of the pork with more glaze. Let rest for 10 minutes then cut into thick slices. Garnish with the chives and scallions and serve.