To make the Tomato Garlic Rasam, combine garlic cloves, black peppercorns, cumin seeds, and coriander stalks in a blender. Grind to a coarse powder. Do not use water to make a smooth paste. Set it aside.
Next, heat ghee or any vegan cooking oil in a heavy bottom kadhai. Add mustard seeds, red chili, curry leaves, and asafoetida. Fry for 10 - 20 seconds or till seeds starts spluttering.
Add chopped tomato, turmeric powder, red chili powder, salt, and cook for 3 - 5 minutes or till tomatoes turn mushy.
Add fresh garlic paste prepared earlier. Stir to combine and cook for a minute.
Add 4 cups of water and rasam masala powder. Stir, and gently mash the tomato using the back of the ladle. At this stage, taste and adjust the seasoning as per personal preference.
Let the rasam simmer over low heat for the next 15 - 20 minutes. Keep stirring at regular intervals. So not cook it for too long.
Garnish with loads of chopped fresh coriander.
Serve with steamed rice or as an appetizer.