Pat oxtails dry, season generously with salt and pepper.

Heat olive oil in a large heavy pot or Dutch oven over medium-high heat. Add oxtails and brown on all sides (about 8–10 minutes). Work in batches if needed. Remove and set aside.

Reduce heat to medium. Add onion and a pinch of salt to the pot; sauté until translucent, 4–5 minutes. Add garlic and cook 30 seconds until fragrant.

Add chopped red peppers and carrots; sauté 2–3 minutes until they begin to soften.

Pour in crushed tomatoes, deglaze the pot with a splash of beef broth, scraping up browned bits (this adds flavor).

Return oxtails to the pot. Add remaining beef broth, bay leaves, thyme, paprika, Worcestershire sauce, and pepper. Bring to a simmer.

Cover, reduce heat to low, and simmer gently for 2–3 hours until the oxtails are fork-tender and the meat starts falling off the bone. (Tip: check at 2 hours — oxtail quality and size affect timing.)

In the last 25–30 minutes of cooking, stir in the butter beans and red wine vinegar. Simmer uncovered so the sauce thickens slightly. If you prefer a thicker stew, remove the lid for the final 15 minutes.

Remove bay leaves and thyme sprigs. Taste and adjust seasoning with salt, pepper, and a squeeze of lemon if desired. Garnish with fresh parsley and a little lemon zest.

Serve hot over mashed potatoes, rice, polenta, or with crusty bread. Enjoy!