Preheat the oven to 325°F (163°C).
Season the short ribs generously with salt and pepper on all sides.
Heat olive oil in a large Dutch oven over medium-high heat. Sear the short ribs in batches until browned on all sides (about 2–3 minutes per side). Remove and set aside.
Sauté aromatics: In the same pot, add chopped onion, carrots, and celery. Cook for 5–7 minutes until softened and beginning to brown. Add garlic and tomato paste, stir for 1 minute.
Deglaze the pot with apple cider, scraping up the browned bits. Let it simmer for 2–3 minutes.
Add beef broth, red wine (if using), Dijon mustard (if using), and herbs (thyme, rosemary, bay leaves, cinnamon stick). Stir to combine.
Return the short ribs to the pot, nestling them into the liquid and vegetables. The liquid should mostly cover the meat.
Cover and braise in the oven for 2.5 to 3 hours, until the meat is fork-tender and falling off the bone.
Remove the pot from the oven, transfer the ribs to a plate, and skim off excess fat from the surface of the liquid.
Optional: Simmer the remaining liquid on the stovetop to reduce and thicken the sauce before serving.
Serve hot, over mashed potatoes, polenta, or crusty bread with a spoonful of the sauce.