How to make tomato rasam?

Ingredients
1/2 cup toor dal
1 cup chopped tomatoes
1 tbsp ghee
1 pinch turmeric powder
2 tsp rasam powder
1 pinch asafoetida
1 tsp mustard
1 tsp cumin seeds
1 tsp chopped garlic
1 tbsp chopped coriander leaves
1/2tsp ground black pepper

Method
1. Soak the toor dal in water for half an hour, pressure cook and mash well.
2. Heat the ghee in a cooking pan. Then add the chopped tomatoes and fry them till they can be mashed.
3. Add the mashed toor dal, 2 cups water, turmeric, asafoetida, rasam powder and salt to taste.
4. When the rasam froths up, season with the given ingredients.
5. Garnish with coriander leaves and ground black pepper.