Slow Cooker Beef Brisket with Red Wine and Caramelized Onion Sauce

Start by combining brown sugar, smoked paprika, cumin, black pepper, and sea salt in a bowl to make the spice rub. Apply the rub generously over the brisket.
Heat the olive oil in a large skillet over high heat. Sear the brisket on all sides until it develops a nice crust. Once seared, place it in the slow cooker.
Reduce the heat to medium using the same skillet and add the thinly sliced onions. Sprinkle them with sea salt and cook, stirring occasionally, for 20-30 minutes or until they become deeply caramelized.
Add the garlic to the skillet and cook for another minute. Pour in the red wine, scraping the bottom of the skillet to lift any browned bits. Cook for a few minutes until the wine is reduced by half.
Stir in the beef broth, then pour this onion-wine mixture over the brisket in the slow cooker. Add the rosemary.
Cook the brisket on low for 8-10 hours or until the meat is tender and can be easily pulled apart with a fork.