Pat short ribs dry and season with salt and pepper.
Heat oil in a Dutch oven, sear ribs on all sides until browned. Remove and set aside.
Add sliced onions to the pot, cook slowly until golden and caramelized (20–25 minutes).
Stir in garlic, tomato paste, and flour, cooking for 1–2 minutes.
Pour in apple cider, scraping browned bits from the pot. Add beef broth, rosemary, thyme, and bay leaves.
Return short ribs to the pot, cover, and transfer to oven at 325°F (165°C).
Braise for 2.5–3 hours, until ribs are tender and nearly falling off the bone.
Remove herbs, adjust seasoning, and serve with mashed potatoes, polenta, or noodles.