Wash the Karpooravalli (Ajwain) leaves thoroughly and gently crush or tear them to release their aroma.
In a small pot, bring 2 cups of water to a boil. Add the chopped tomato and tamarind pulp. Allow it to cook until the tomato becomes soft.
Add turmeric powder, rasam powder, and a pinch of salt to the pot. Stir well and let it simmer for a few minutes.
In a separate pan, heat oil over medium heat. Add mustard seeds and cumin seeds, allowing them to splutter. If using, add crushed garlic and sauté until it turns golden.
Add asafoetida and curry leaves to the tempering. Quickly pour this tempering into the simmering rasam.
Add the crushed Karpooravalli leaves to the rasam and let it simmer for another 5–7 minutes. This will infuse the rasam with the healing properties of the leaves.
Taste and adjust salt if needed. Turn off the heat and garnish with freshly chopped coriander leaves.
Serve the warm Karpooravalli Rasam to your child, either as a soup or mixed with a small portion of rice.