Step 1: Marinate the Beef

• In a bowl, combine the beef cubes with vinegar, tamarind paste (if using), salt, sugar, and turmeric. Mix well to coat the beef.
• Cover and marinate in the refrigerator for at least 1 hour, preferably overnight for deeper flavor.

Step 2: Prepare the Vindaloo Sauce

• Heat the vegetable oil in a large pot or Dutch oven over medium heat.
• Add the chopped onions and sauté until golden brown, about 5-7 minutes.

Step 3: Add Aromatics

• Stir in the minced garlic, ginger, and green chilies. Cook for an additional 2 minutes until fragrant.

Step 4: Incorporate Spices

• Add the cumin, coriander, black pepper, cinnamon, mustard seeds, fenugreek seeds, and dried red chilies. Stir well to toast the spices for about 1-2 minutes.

Step 5: Cook the Beef

• Add the marinated beef to the pot, stirring to coat with the spice mixture.
• Pour in the beef broth, bring to a boil, then reduce the heat to low. Cover and simmer for about 1.5 hours, or until the beef is tender and the sauce has thickened.

Step 6: Serve

• Once cooked, taste and adjust seasoning if needed. Garnish with fresh cilantro and serve hot with rice or naan.