Marinate the Beef: In a large bowl, mix 2 lbs of beef stew meat with the marinade ingredients: 1 tbsp white vinegar, 2 tsp red chili powder, 1 tsp turmeric, and 1 tsp ground cumin. Make sure the beef is well-coated, cover, and refrigerate for at least 1 hour, preferably overnight for best results.
Prepare the Spice Blend: In a small bowl, combine 2 tbsp ground coriander, 1 tbsp ground cumin, 1 tbsp paprika, 1 tsp turmeric, 2 tsp garam masala, 2 tsp cayenne pepper, 1 tsp ground cinnamon, and 1 tsp ground cardamom. Set this mixture aside as it will be added later.
Sauté Aromatics: In a large pot, heat 3 tbsp of vegetable oil over medium heat. Add 2 medium onions, finely chopped, and sauté until golden brown. This should take about 5-7 minutes. Then, add 4 minced garlic cloves and 1-inch grated ginger, cooking until fragrant, which should take another minute.
Add Spices: Stir in your spice blend and cook for an additional 1-2 minutes to allow the spices to release their flavors, stirring frequently to avoid burning.
Add Tomatoes: Pour in the 2 medium pureed tomatoes and cook the mixture until it thickens, which should take about 5-7 minutes.
Brown the Beef: Take the marinated beef from the refrigerator and add it to the pot. Sear the beef on all sides until it's well browned, locking in flavors, approximately 5-10 minutes.
Simmer the Curry: Stir in 3 tbsp of white vinegar and 1/2 cup of water or beef stock. Bring the mixture to a boil, then reduce the heat and let it simmer on low for 1-1.5 hours, or until the beef is fork-tender. You can add more water if necessary during cooking.
Garnish and Serve: Once the beef is tender, remove from heat, garnish with 2 tbsp of chopped cilantro, and serve hot alongside steamed rice, naan, or parathas.