Preheat the oven to <temperature>225<unit>°C</unit></temperature>

Place <quantity>1.5<unit>kg</unit></quantity> of oxtail into 2 roasting pans and brush the tails with extra virgin olive oil

Peel and chop <quantity>4</quantity> medium carrots. Place in another roasting pan

Halve, peel, trim and chop <quantity>4</quantity> medium red onions. Place them in the roasting pan with the carrots

Roughly chop <quantity>2</quantity> tomatoes and add to the vegetables roasting pan

Add <quantity>10<unit>stalks</unit></quantity> of lemon thyme and drizzle the vegetables with extra virgin olive oil

Place the roasting pans with the vegetables and the oxtail in the oven. Roast the vegetables for 20m until golden brown

Roast the oxtail for another 15m until golden brown

Transfer the oxtail to a large pot

Add the roasted vegetables

Add <quantity>5<unit>L</unit></quantity> of water and place the pot over medium heat

Remove impurities from the broth with a sieve from time to time

Simmer over low heat for 5h to reduce and concentrate the flavors

Strain and transfer to another pot

Simmer the strained broth, removing the impurities from time to time

Reduce to an amber-colored, flavorful liquid

Season with salt and black pepper to taste. The beef bone broth is ready

Add some chopped coriander. Enjoy!