Bring the brown sugar, salt, bay leaves, 1 tablespoon coriander seeds, whole cloves, and 2 cups water to a boil in a medium saucepan. Reduce heat to a simmer and stir occasionally, until sugar and salt dissolve.
Pour brine in a large bowl along with 2 cups of ice and the apple cider and let cool.
Roast
Place the pork loin and brine in a 2-gallon bag and seal. Chill in the fridge for a minimum of 8 hours or overnight.
Remove the pork from the brine when ready to cook, pay dry with paper towels, and let sit for 1 hour.
Toss potatoes and onions with 1/4 cup olive oil and season with salt and pepper.
Place the rack in the lower third of the oven; preheat to 425 ℉.
Crush the remaining 2 tablespoons of coriander seeds with a mortar and pestle or the side of a chef’s knife. Rub pork with salt, pepper, and crushed coriander. Tie kitchen twine around the meat at 1-inch intervals.
Heat the remaining 1 tablespoon of olive oil in a large skillet and brown the pork on the sides, about 8 to 10 minutes.
Transfer pork to roasting pan and place potatoes and onions around the meat. Tuck additional Bay Leaves into the twine on top. Cook for 60 to 75 minutes or until the pork reaches an internal temperature of 140 ℉.
Remove from oven and let sit for 30 minutes before slicing.
Notes
You can brine the pork up to 2 days before cooking. Keep chilled.