Soak chana dal for 30 mins. Pressure cook chana dal with double the amount of water until cooked but still maintains the shape (about 15- 20 minutes in a traditional pressure cooker or 1 whistle).
In a pan, heat the oil, add cumin seeds, saute until it begins to splutter. Add onions and fry till golden brown. Add ginger and garlic and fry for about 2 minutes. Add tomatoes, turmeric powder, coriander powder and salt to taste. Mix well and fry on medium heat until masala thickens, and oil begins to separate. Add the boiled Chana dal with the leftover water from the cooker and mix well.
Cook on medium heat for about 10 minutes until dal begins to look consistent but still maintains the shape.
Add garam masala and cook for one minute. Mix well and remove from heat.