Prepare the black beans: If using dried black beans, soak them in water overnight. Drain before using. Alternatively, use canned black beans for a quicker recipe.
Cook the beans: In a large saucepan or pressure cooker, heat oil over medium heat. Add cumin seeds and sauté until fragrant. Add chopped onions and cook until golden brown.
Add spices and tomatoes: Stir in ginger, garlic, and chopped green chili. Cook for a minute, then add the coriander powder, turmeric powder, red chili powder, and salt. Stir well.
Simmer the curry: Add the pureed tomatoes and cook for 5 minutes. Add the soaked and drained black beans, followed by water. Bring the mixture to a boil. If using a pressure cooker, cook for 2-3 whistles. If using a saucepan, cover and simmer for 45 minutes or until the beans are tender.
Finishing touches: Once the beans are cooked and tender, add garam masala and simmer for another 5 minutes. Garnish with fresh cilantro before serving.
