Preheat your oven to 325°F (163°C).
In a large skillet, heat the olive oil over medium heat. Add the sliced onion and sauté until translucent, about 5 minutes. Stir in the minced garlic and cook for an additional minute.
In a large bowl, combine the cranberries, beef broth, brown sugar, soy sauce, Worcestershire sauce, thyme, black pepper, and salt. Mix well.
Place the brisket in a roasting pan and pour the cranberry mixture over it. Spread the sautéed onions and garlic on top of the brisket.
Cover the roasting pan tightly with aluminum foil and bake in the preheated oven for 3 to 4 hours, or until the brisket is tender.
Remove the foil and bake for an additional 30 minutes to caramelize the top.
Once done, let the brisket rest for 15 minutes before slicing against the grain. Serve with the cranberry sauce drizzled on top.