Cook pineapple, tomatoes, dhal, pepper powder, rasam powder with a pinch of turmeric powder and salt in 3.5 cups of water. Cook till the raw smell of rasam powder is gone. Add a pinch of hing and simmer it for 1-2 mins.
Season it with cumin, garlic, curry leaves and mustard seeds roasted in ghee.
Add lemon juice. Garnish with coriander. Serve hot and enjoy.