1. Preheat oven to 325°F (160°C).

2. Season short ribs generously with salt and pepper.

3. In a large Dutch oven, heat olive oil over medium-high heat.

4. Sear short ribs on all sides until well browned, then remove and set aside.

5. Add onion, carrots, and celery; sauté until softened.

6. Stir in garlic and tomato paste; cook for 1 minute.

7. Sprinkle in flour and stir to coat vegetables.

8. Pour in apple cider, scraping up any browned bits from the bottom.

9. Add beef broth, apple cider vinegar, rosemary, thyme, and bay leaves.

10. Return short ribs to the pot, making sure they are mostly submerged.

11. Bring to a simmer, cover, and transfer to the oven.

12. Braise for 2½ to 3 hours, until meat is tender and falling off the bone.

13. Remove ribs and strain sauce; simmer sauce to thicken if desired.

14. Serve ribs with mashed potatoes or creamy polenta, topped with sauce.