Oxtail Ragu

Ingredients

• 3 1/2 pounds beef oxtail, cut into 2-inch sections
• 1 tablespoon olive oil
• Salt and freshly ground black pepper
• 1 large yellow onion, diced
• 6 cloves garlic, roughly chopped
• 1/4 cup sherry vinegar
• 4 cups tomato sauce or puree, or more if desired
• 2 cups chicken broth, or enough to cover the oxtails
• 1 sprig fresh rosemary
• 2 sprigs fresh thyme
• 2 sprigs fresh oregano
• 1 teaspoon kosher salt, plus more to taste
• 1/4 teaspoon red chili flakes