Add the beef stew meat, lentils, onion, carrots, garlic, and ginger to the slow cooker.
Sprinkle in the cumin, turmeric, and garam masala, then pour in the beef broth and diced tomatoes.
Stir everything together until the spices are evenly distributed.
Cover and cook on low for 8 hours, until the beef is tender and the lentils are soft.
Stir in the salt and black pepper, then taste and adjust seasoning if needed.
Ladle into bowls and top with the chopped cilantro before serving.