Heat oil in a large skillet or saucepan. Add the cumin seeds and when they start to crackle, add the onion, ginger and garlic. Saute until golden brown. Add tumeric, salt and cayenne to cooked onion and cook another 30 seconds. Add spinach and cook for 3 minutes. Now add daal and bring to a boil. Cover, reduce heat and cook for 40 minutes or until daal is tender and of creamy consistency. Check periodically to see if more water is necessary. Remove from heat and stir in the coriander. Garnish with garam masala