Rasam (Thin Tamarind and Pepper Broth)

Variations

• Tomato rasam: halve the tamarind and use four tomatoes. Much gentler, and the version children eat.
• Puli rasam (tamarind only): no dal at all, just tamarind water, water and spices. The thinnest and sourest form, and the one made when somebody has a cold.
• Pineapple or lemon rasam: the sourness comes from somewhere else — but lemon juice goes in only after the heat is off. The reason is in the Tips, and it reverses there.
• Rasam powder: coriander seed, pepper, cumin, dried chilli and a little toor dal, roasted and ground, saves the pounding each time. It noticeably fades after a month.
• Beside sinigang: another broth soured with tamarind, aimed differently. Sinigang is a soup with things in it — pork and vegetables are the point; rasam keeps almost no solids and is a broth you drink.

Tips

• Which acid it is decides the order of the recipe. Tamarind's acidity is mostly tartaric. Unlike the acetic acid of a vinegar or the lactic acid of a ferment it does not volatilise, so simmering does not blow the sourness off. That is why the tamarind goes in at the start and gets eight to ten minutes to lose its raw edge — and why the lemon version has to do the exact opposite and go in last. When the acid is added is not a preference; it follows from which acid it is (balancing flavour).
• Not in aluminium or bare cast iron. Tartaric acid is a chelator: it grabs metal ions, so an aluminium pot puts a metallic edge in the broth and comes out stained. Stainless, enamel, or the traditional South Indian tin vessel.
• It is taken off at the froth, not at a boil. Stocks and broths asks for no boiling in the name of clarity; here it is a question of aroma. The pepper and curry leaf the tadka just delivered are volatile and a minute of hard boiling takes much of it away — and the dal starch, boiled on, settles out and leaves the broth heavy.
• The pepper is cracked coarse for the same reason. Ground fine it has far more surface area, loses its aroma faster, and disperses into the liquid as a muddy dust. Coarse fragments release slowly and are still doing it at the table.
• The tadka is not a last ingredient, it is a last cooking step. Exactly as blooming spices sets out: mustard seeds open only by popping in fat, and curry leaves hand over their aroma the moment they hit it. Dropped into the broth, neither does much at all. Note the difference from dosa, which pops the same mustard seeds all the way to destroy their pungency; here it stops at ten seconds.
• The dal is the liquid, not the ingredient. Dal exists to break the pulses down into body; rasam uses only the water they cooked in. What is left behind becomes the next meal's dal — one pot, two dishes.
• How thin is thin. If a spoon leaves a trail, it is too thick. Poured over rice it should run straight down between the grains.