Rasam Recipe: Why You Must Never Boil It Hard

Rasam is the opposite of sambar in almost every respect. Sambar is thick, substantial, full of vegetables, and it improves overnight. Rasam is thin enough to drink from a tumbler, sharp with tamarind and pepper, and it is at its best within twenty minutes of being made. Where sambar is the middle of a meal, rasam is near the end, spooned over a small mound of rice to settle everything that came before.

There is one rule that matters more than every other instruction here, so I will put it at the top: rasam must never be boiled hard. You bring it to the point where a pale froth rises to the surface, and then you take it off the heat. That is it. Boiling past that point drives off the aromatics you just spent the recipe building, and leaves a dull, flat liquid that tastes of nothing but sour.

Why the Froth Rule Exists

Rasam's flavour lives almost entirely in volatile compounds: the crushed pepper and cumin, the asafoetida, the curry leaves, the fresh coriander. These are exactly the compounds that evaporate first. A rolling boil for even two or three minutes strips most of them out.

Watch the surface instead of the clock. As the rasam approaches a simmer, a layer of pale foam gathers and the liquid begins to look cloudy and lively rather than still. The moment that froth covers the surface, turn the heat off. The residual heat finishes the job.

Ingredients

• Tamarind, a small lime-sized ball soaked in 1.5 cups hot water, squeezed and strained
• 2 ripe tomatoes, roughly crushed by hand
• 1/4 cup cooked toor dal, mashed thin with water (optional but traditional)
• Rasam powder, 2 teaspoons (see below)
• Turmeric, 1/4 teaspoon; salt to taste; a small piece of jaggery
• Fresh coriander, a generous handful, chopped
• For tempering: 2 tablespoons ghee or sesame oil, 1 teaspoon mustard seeds, 1 teaspoon cumin, 2 dried red chillies, a sprig of curry leaves, a good pinch of asafoetida

Rasam Powder, Made Fresh

Rasam powder differs from sambar powder in being much heavier on pepper and cumin and much lighter on coriander. You can buy it, but a small quantity ground fresh for a single pot is dramatically better, and it takes five minutes.

Dry-roast until fragrant: 1 tablespoon coriander seeds, 1 teaspoon black peppercorns, 1 teaspoon cumin seeds, 2 dried red chillies, 1/4 teaspoon fenugreek. Cool, then grind coarse, not fine. A slightly coarse grind gives rasam its characteristic texture on the tongue.

Some households add two cloves of garlic crushed with the pepper. It is not universal, but it is very good.

Method

1. Put the strained tamarind water in a pot with the crushed tomatoes, turmeric, salt, jaggery and rasam powder. Simmer gently for six to eight minutes, until the raw smell of tamarind has gone and the tomatoes have broken down. This is the only stage that gets sustained heat.
2. Stir in the mashed dal and enough water to bring it to the consistency of a thin soup. It should be properly thin; rasam that coats a spoon is too thick.
3. Heat gently. Watch for the froth. The moment the surface is covered in pale foam, turn off the heat. Do not let it reach a rolling boil.
4. Make the tempering in a small pan: heat the ghee, pop the mustard seeds, add cumin, chillies, curry leaves and asafoetida, and as soon as the leaves crackle, pour it over the rasam.
5. Stir in the chopped coriander and cover for two minutes before serving.

Versions Worth Knowing

Pepper rasam (milagu rasam) drops the tomato entirely and doubles the pepper and cumin. It is what gets made in South Indian households when somebody has a cold, and it is genuinely restorative — thin, hot and aromatic.

Tomato rasam goes the other way: more tomato, less tamarind, sometimes none at all, relying on the tomatoes for sourness. Milder and a good introduction if you find classic rasam too sharp.

Lemon rasam uses no tamarind. The dal and tomato base is cooked, then lemon juice is stirred in off the heat. Never add lemon to a pot still on the flame; it turns bitter.

Garlic rasam (poondu rasam) uses a dozen crushed cloves added at the tamarind stage. Pungent and excellent with plain rice.

Troubleshooting

How It Is Eaten

In a traditional meal, rasam comes after sambar. A small amount of rice is served, rasam is poured over it, and it is eaten quickly while hot, often with a fried pappadam and a spoonful of vegetable poriyal on the side. Some people drink the last of it straight from a tumbler, which is the best argument for making it thin.

For the full sequence of a rice meal and where rasam sits in it, see our guide to the South Indian thali.