Heat Ninja on High Oven Heat mode with the olive oil. Add the onions and cook, stirring frequently, for about 20 minutes or until the onions have caramelized lightly.

While the onions are cooking, take the brisket out of its packaging and pat it dry. Season the meat generously with salt and pepper.

Remove onions and sear the brisket until a golden brown crust appears on both sides of the meat. Remove brisket.

Place raw vegetables on bottom of Ninja.  Put brisket on top (fatty side up) and top.  Sprinkle the minced garlic and carmelized onions over the meat.

Mix the broth, Worcestershire sauce, and soy sauce, and pour into Ninja.

Cover and cook in the LOW for 6 to 8 hours or until the brisket is very tender. Let rest for at least 20 minutes before serving in the slow cooker set on WARM. (If your slow cooker doesn't have a WARM setting, transfer to a baking dish and cover tightly with foil while resting.)

The brisket can be sliced or shredded immediately and served with the onions and juices. Or let the meat cool then refrigerate overnight. Before reheating, scrape away and discard the layer of fat that has formed around the meat.