Place the skillet in the oven on a middle rack and preheat the oven to 450 degrees F. The skillet will heat along with the oven.
Pat the pork dry with a paper towel and set aside. Combine the tarragon, coriander, ginger, salt, and pepper in a small bowl. Rub the spice mixture onto all sides of the pork.
Carefully remove the hot skillet from the oven using oven mitts and pour the oil in the pan. Swirl to coat the bottom.
Place the pork in the pan. (You can bend the pork to fit the pan if it's a little long). Return the pan to the oven. Roast for 10 minutes.
Flip the pork to the other side. Reduce the oven temperature to 400 degrees F and continue roasting another 15 minutes. The pork is done with it's internal temperature registers 145 degrees in the thickest part of the meat.
Transfer the pork to a large plate and cover with foil. Let the pork rest while you make the glaze.
TO MAKE THE GLAZE
Sprinkle the sugar in a small skillet and cook over medium-high heat until dark amber, about 5 minutes.
Remove from the heat and whisk in the juice, vinegar, tarragon, ginger, marmalade and zest.
Return to medium-low heat and boil until thick, stirring, about 5 minutes.