Mexican Stuffed Lamb With Spiced Tomato and Olive Sauce

Ingredients

• 2 pounds (8 small) roma tomatoes, halved lengthwise and quartered
• ½ cup tomato paste
• 3 tablespoons tamarind concentrate
• 1 tablespoon olive oil
• 1 tablespoon sugar
• 4 garlic cloves, minced
• 2 small dried chile de árbol
• 1 large yellow onion, roughly chopped
• 1½ cups pitted kalamata olives
• 1 cup fresh cilantro leaves
• Kosher salt, to taste
• 2 tablespoons olive oil
• 1 large yellow onion, finely chopped
• 3 garlic cloves, minced
• 1½ pounds ground lamb
• 1 cup long-grain white rice
• 5 small dried chile de árbol
• 1 small plum tomato, roughly chopped
• Pinch of freshly grated nutmeg
• 2 cups beef broth
• 1 cup water
• One 3½-pound lamb shoulder
• 4 celery stalks, roughly chopped
• 2 large carrots, roughly chopped
• 3 cups beef broth
• 1 pound small new potatoes, preferably multi-color
• ½ cup cilantro stems