Preheat the oven to 250°Line 2 rimmed baking sheets or casserole dishes with parchment paper. Set aside.
Pat the brisket dry and cut into 2 pieces, against the grain (see Kitchen Tips), so that they will fit into a large cast-iron pot or enamel-coated cast-iron pot. Rub the the meat on both sides with the ras al hanout spice mixture and 1 tablespoon of the salt. Place on one of the prepared baking sheets or casserole dishes.
Heat the oil in that cast-iron large pot over high heat until it shimmers. Place one piece of the seasoned brisket into it, fat side down, and cook for 1½ to 2 minutes, until browned on one side (no need to turn). With tongs, transfer to the second (cleabaking sheet. Place the second piece of brisket, fat side down, into the pot to cook for 1½ to 2 minutes. Transfer to the baking sheet with the first piece. Reserve the pot and its contents.
Reduce the heat to medium, add the onions to the pot, and cook, stirring, for 7 to 9 minutes, until they are translucent and the edges have browned.
Add the garlic and cook, stirring, for 15 to 20 seconds. Add the vinegar and stir well, scraping up all the flavorful browned bits at the bottom of the pot, and being very careful of the powerful fumes that will rise when you add the vinegar. Cook for 1½ to 2½ minutes, until the mixture comes to a boil, and add the stock, half the pomegranate molasses, and the sugar and stir very well. Cook for about 2 minutes, until the sugar begins to dissolve. Turn the heat off and return the brisket pieces to the pot. Cover tightly with heavy-duty foil and then a lid, and place in the oven to cook for 2 hours.
With oven mitts, remove the pot from the oven. Uncover and discard the foil. Add the carrots, sweet potatoes, and dried fruits, cover tightly with fresh foil, and replace the lid. Reduce the oven temperature to 225°F, return the pot to the oven, and cook for 8 to 9 more hours (this works great overnight!!!), until the meat is fork tender and the fruit is very soft and plump.
With kitchen towels or oven mitts, carefully remove the pot from the oven and let stand, still covered, for about 20 minutes, until cool to the touch. Refrigerate for 18 to 24 hours and up to 3 days.
About 2 hours before serving, preheat the oven to 265°Remove the tsimmis from the refrigerator, uncover, and discard the foil. Skim all the visible fat from the top and around the edges and discard. Cover with fresh foil and heat in the oven for 2 hours, or until thoroughly warmed.
While the tsimmis is heating, line a fine-mesh sieve with 2 layers of cheesecloth.
When the tsimmis is warmed through, with kitchen towels or oven mitts, carefully remove the pot from the oven. Discard the foil and transfer the brisket to a work surface. Cut the brisket across the grain into ⅛- to ¼-inch thick slices and place on a serving platter. Using a slotted spoon, scoop the fruit and vegetables onto the platter.
Ladle the cooking liquid through the prepared fine-mesh sieve over tsimmis. Drizzle the brisket with the remaining pomegranate molasses, and serve immediately.