Pat roast dry and season all over with kosher salt*, set aside.
Preheat dutch oven, add oil and when it's hot sear the pork on all sides, turning as each side gets good color. Don't rush this step! It could take 10 minutes to get all the sides browned.
When roast is browned remove to a plate, reduce heat to medium and add onions. Cook and stir until onions are all golden and soft (but not burned), about 15 minutes. Add smashed garlic and stir 1 minute.
Add marsala and stir 30 seconds. Add cider, dijon, broth, salt and a good amount of cracked pepper. Stir well and then nestle the pork into the liquid. It should only partially come up the sides of the pork. Scoop some of the onions and liquid onto the top of the pork and place the rosemary springs around it.
Cover the pot and place in a 325°f oven. Cook for 2 and 1/2 to 3 hours, checking at the 2 and 1/2 hour mark to see if it's done*
Remove pork to a platter and cover loosly with foil to keep warm. Return pot to the stovetop, remove the rosemary and discard, smash garlic into the drippings with the back of a fork, and bring to a boil. Simmer until it's slightly thickened to a nice sauce consistency.
Break pork apart into serving size pieces and pour sauce/onions over the top.
Enjoy!