In a large pot or bowl, combine salt, sugar, water, peppercorns and bay leaves. Submerge pork loin in mixture and let brine for about 4 hours. Preheat oven to 375 degrees F. Remove pork loin from brine and dry well. Season well with Gray salt and freshly ground black pepper.
Heat 2 tablespoons of olive oil in the bottom of a heavy, stove top and oven-safe casserole dish over medium-high heat. Brown pork well and place in preheated oven to cook about halfway, about 35 minutes. Meanwhile, heat 1/4-cup olive oil in a medium saute pan over high heat. Add shallots and cook until they begin to caramelize, about 8 minutes. Turn heat to medium and season with salt and pepper. Add rosemary and let cook until golden brown (about 10 minutes more). Add marmalade and stir to combine. Remove from heat and set aside.
After 35 minutes, remove pork from oven and spoon half the shallot mixture over the top and sides of the pork. Place back in the oven and continue to roast until a meat thermometer (inserted into the center of the pork) reads 165 degrees F (about 30 minutes more). Remove and let rest 15 minutes before carving. Serve with reserved shallot mixture on the side.
Substitute orange marmalade or any other flavor for the Meyer Lemon Marmalade in this recipe.