2. Season the short ribs with salt and pepper on all sides.
3. Heat the olive oil in a large skillet over medium-high heat. Add the short ribs and brown them on both sides, then remove from the skillet and set aside.
4. In the same skillet, add the diced onion and minced garlic and cook until softened, about 5 minutes.
5. Stir in the beef broth, red wine, brown sugar, tomato paste, thyme, and rosemary and bring to a simmer.
6. Add the short ribs back into the skillet and pour the sauce over them.
7. Transfer the skillet to the slow cooker and cook for 8-10 hours on low or high for 4-6 hours.
8. Once cooked, remove the short ribs from the slow cooker and let them rest for 10 minutes before serving.