Preheat your oven to 160°C (320°F). Pat the oxtail pieces dry with paper towels, then season generously with salt and black pepper on all sides. This helps the meat brown more effectively, enhancing the stew's rich flavour.

In a large Dutch oven or heavy bottomed pot, heat 2 tablespoons of olive oil over medium high heat. Working in batches, sear the oxtail pieces on all sides until they are deeply browned. Set aside the browned pieces on a plate as you go, adding more oil if necessary.

Add the remaining olive oil to the pot. Lower the heat to medium, then add the chopped onion, carrots, celery, and red bell pepper. Sauté for about 8-10 minutes until the vegetables soften and the onions become translucent. This step builds the base flavour for the stew.

Add the minced garlic to the pot and stir for another 1-2 minutes until fragrant. Sprinkle the flour over the vegetables, stirring constantly to cook out the raw taste for 2 minutes. This helps thicken the stew.

Pour in the red wine, using a wooden spoon to scrape up any browned bits from the bottom of the pot. Let the wine simmer for 5 minutes to reduce slightly, intensifying its flavour.

Return the browned oxtail pieces to the pot. Add the beef broth, bay leaves, rosemary, smoked paprika, cumin, and grated tomato. Stir well, ensuring the oxtail is submerged in the liquid. Bring the stew to a gentle simmer.

Cover the pot with a lid and transfer it to the preheated oven. Let it cook for 3-4 hours, or until the oxtail meat is tender and falls off the bone. Check occasionally to ensure there’s enough liquid, adding a bit more broth if necessary.

Remove the pot from the oven and discard the bay leaves and rosemary sprig. Serve the Rabo de Toro hot, garnished with fresh parsley. Accompany with crusty bread or Spanish potatoes to soak up the rich sauce, and pair with a glass of red wine to elevate the experience.