Remove the brisket from the fridge 30 minutes before cooking to allow it to come to room temperature. While it rests, drizzle olive oil over the meat and generously rub in the spice mix of salt, black pepper, dried thyme, dried rosemary, garlic powder, and onion powder.

Dice half of the yellow onion and thinly slice the other half. Gather your minced garlic, shallot, and prepared onions for sautéing.

In a saucepan, heat a tablespoon of olive oil over medium heat. Add the diced onion, shallot, and minced garlic, cooking for about 5 minutes until the onions become translucent.

Stir in the cranberry jelly, Worcestershire sauce, and Guinness, letting it simmer for an additional 10 minutes until the sauce thickens slightly.

Preheat the oven to 250°F (120°C).

Pour half of the prepared sauce into a roasting pan and add the sliced onions. Place the brisket, fat side down, into the pan and pour the remaining sauce over the top.

Surround the brisket with red potatoes and dried cranberries, then cover the pan tightly with aluminum foil.

Roast the brisket in the preheated oven for approximately 4 hours.

Once done, remove the brisket from the oven and let it rest, covered, for 30 minutes before slicing against the grain to serve.