Heat the oven to 325°F. Combine the ginger, turmeric, paprika, black pepper, cinnamon, chili powder, cayenne pepper, and salt. Reserve 2 teaspoons for the vegetables. Sprinkle the brisket with this mixture and rub in the minced garlic.

Heat 3 tablespoons of olive oil in a large Dutch oven or pot. Sear the beef all around. Remove from the Dutch oven and set aside.

Add the diced onion and bell pepper to the oil in the pan and season with the reserved 2 teaspoons of seasoning. Saute until the onion is translucent, add the tomatoes, mix and cook for about 5 minutes.

Add the brown sugar and stock, horseradish, bay leaves, and thyme. Pour out of the pan into a bowl. Place the red onion rings in the bottom of the pan and sprinkle with the remaining tablespoon of olive oil.

Place the brisket on top of them. Pour the vegetables and stock over the brisket. Add the cubed sweet potatoes to the pot.

Cover and bake in the preheated oven for 3 ½ hours, until the brisket is fork tender. Remove the brisket, cool, and refrigerate. Once the brisket is chilled, remove excess fat and then slice against the grain. If desired, make the brisket a day before you plan to serve it, and cool overnight. Slice and reheat before serving.

Place the sliced brisket in a pan or pot, cover with sauce. Heat for half an hour or more in the oven at 300°F, or until heated through.