• Trim the fat cap off the brisket, leaving just 1/3 inch. Cut into 3-inch cubes.
• Add the brisket to the slow cooker along with the remaining ingredients and 2 teaspoons salt.
• Cook on low for 8 hours. Remove to a bowl and shred. Return to the slow cooker and keep warm until ready to eat.
• Serve alongside taco fixings or as a topping for Mexican brown rice.

To make in the oven:

• Preheat the oven to 350 degrees F.
• Place a large Dutch oven over high heat.
• Trim the fat cap off the brisket, leaving just 1/3 inch. Cut into 3-inch cubes. Season the brisket with salt and pepper. Sear the brisket fat-side down until nicely browned, about 2 minutes on the first side. Brown the brisket on the additional sides, about 1 minutes per. Remove to a plate. Add the cider and scrape up the brown bits from the bottom of the pan. Stir in the cumin, paprika, chili powder, cinnamon, garlic, and 2 teaspoons salt. Return the beef to the pot, fat-side up. Pour in enough water to come at least 2/3's of the way up the beef.
• Cover and braise in the oven for 2 hours, until tender. Remove the lid and cook for an additional 1 to 1.5 hours, until nearly falling apart. Shred with two forks and keep in the marinade until ready to eat.