How to make the perfect tomato rasam – recipe | Indian food and drink

According to the Times of India, “no south Indian meal is complete without rasam. Also known as Saaru & Chaaru in Kannada & Telugu languages, it’s a simple appetiser recipe that increases your hunger.” The word means juice, or extract, which should give you some idea about the consistency of this tangy broth, which, as Cyrus Todiwala explains, is “sipped both to add flavour and aid digestion”.

J Inder Singh Kalra describes it as “an appetizer-cum-digestive-cum-accompaniment”, a versatile dish that comes in many flavours – Chandra Padmanabhan’s book of South Indian vegetarian recipes, Dakshin (which was gifted to me by the Guardian’s own Meera Sodha), for example, contains no fewer than 10 different recipes, from buttermilk to garlic – but even within the tomato variation that I’ve picked to make the most of seasonal produce, Sanjeev Kapoor notes that every bowl “will always have the imprint of the cook, since everyone makes it differently”. Here’s the way I like it.

To pulse or not to pulse

Most of the recipes I try include pulses of some kind, commonly toor dal or split pigeon peas, though Meera Sodha uses the quicker cooking red lentil for the temple tomato rasam in her book Fresh India. Only Eleanor Ford’s the Nutmeg Trail eschews them altogether, which makes for a thinner, more elegant result, but the general consensus among my testers is that the earthy sweetness of the pulses is a nice counterbalance to the sour elements and, even in a recipe designed to refresh, a little bulk is welcome.

That said, if you fancy a smoother soup, you may prefer, as Kapoor suggests in his book How to Cook Indian, to discard the dal itself and use only the liquid it’s been cooked in, which, as we discovered with aquafaba meringues, is likely to be surprisingly rich in protein. Alternatively, you could put the cooked dal though a food mill or strainer for a thicker finish, but I like the chunkier consistency of Padmanabhan and Sodha’s versions, and the nuttiness of the toor dal over the sweeter red lentil ones – though, if you’re in hurry, you might want to swap in the latter.

Make sure you don’t drain the lentils, though, or let them boil too dry, because their cooking water is an important element of this dish. If you like, you can leave out the fresh green chilli and use a dried chilli in the broth for more heat.

The tomatoes

Everyone uses fresh tomatoes, which I imagine are good year round in south India, but I can’t see why you couldn’t substitute the chopped tinned variety out of season elsewhere. Bear in mind, though, that you might need to add more tamarind to balance their sweet jamminess.

Rather than simply chopping the tomatoes, Kalra purees them in the recipe in his book Prashad, which makes them easier to reduce, and so intensifies the tomato flavour – something that may be particularly helpful with more subtle fruit. That said, I hate extra washing-up, so if you’ve got the grater out for the ginger and garlic anyway, you may as well use that on the tomatoes, too, and discard the skins, which will be helpfully left in your hand afterwards.

The spices

Many recipes call for rasam powder – a readymade spice mix that usually includes asafoetida, black pepper, red chillies, coriander and cumin, as well as toasted dal as a thickener; Kapoor’s version also uses curry leaves. As with all such blends, however, it’s hard to make in small quantities and best used fresh, so unless you’re going to be making a lot of rasam, it seems to make more sense just to add what you need.

Rasam, like many such dishes, relies on a tadka, for which whole spices are tempered in hot fat and the subsequent infused oil used to season the whole pot. It seems more common to start the recipe with this, but stirring in the tadka at the end, as Kapoor recommends, gives a fresher, more pungent result. (If you don’t want to use another pan, feel free to go down the traditional route and start with it instead.)

The flavour profile is hot and peppery: brown mustard seeds and black pepper are nearly ubiquitous, while curry leaves, turmeric and cumin seeds add an earthy bitterness. I’ve left out the fiery dried red chillies used by Kapoor and Kalra, given there’s a fresh one in the dal, but if you taste the dish and find you’d prefer it hotter, try adding a pinch of Ford’s chilli powder.

The sweet heat of ginger, as deployed by both Sodha and Padmanabhan, always pairs well with sharper notes, while the funk of garlic and asafoetida give the soup depth.

The sour

Padmanabhan explains that her recipe is for a “mild, gentle rasam without tamarind and rasam powder”, and advises those seeking a tangier flavour to add more tomatoes. You could certainly do that, but it seems to me much easier, and more effective, to use tamarind water or paste, as everyone else does – the latter is more easily available in British retailers, but varies wildly in strength, so stir it in bit by bit and taste as you go.

Perfect tomato rasam

Prep 15 min
Cook 1 hr
Serves 2-4

75g toor dal
1 green finger chilli, or 2 if you like more heat
1½ tbsp coconut or vegetable oil or ghee
30g fresh ginger, peeled and finely grated
2 garlic cloves, peeled and finely grated
4 tomatoes, coarsely grated (discard the skins)
½ tsp turmeric
½ tsp ground black pepper
Salt, to taste
2 tbsp tamarind paste (see introduction)
1 tsp black mustard seeds
1 tsp cumin seeds
A pinch of asafoetida
A few curry leaves
Chopped coriander leaves, to garnish

Rinse the dal well in cold water, then put it in a small pan with 250ml cold water and the green chilli, slit down its length (if using two chillies for a spicier result, finely chop the second one and add that to the pan later at the same time as the garlic and ginger).