South India's cooked chutney — tomatoes reduced to a jammy concentrate with dried chilli, finished with a mustard-curry leaf tempering. The dosa chutney when coconut is unavailable.
Tomato chutney is a cooked chutney — the tomatoes must reduce completely until they stop simmering and start frying in the oil. This transition from water-based simmering to oil-based frying is the most important moment in the recipe. Before it, the chutney tastes of fresh tomato. After it, it tastes of concentrated, caramelised, Maillard-developed tomato — a completely different flavour. The reduction is not just about concentration, it is about chemical transformation.
Heat oil. Fry dried chillies, garlic, ginger 1 minute. Add onion, cook 5 minutes. Add tomatoes and salt. Cook on medium-high, stirring frequently, until all moisture evaporates and the mixture starts frying in the oil — about 15 minutes total. The colour should deepen to a brick-red concentrate.
The transition from water-based simmering (100°C maximum) to oil-based frying (150–180°C) occurs as the last free water evaporates. Above 120°C, Maillard reactions between the tomato amino acids and reducing sugars produce pyrazines and furans — compounds that give the chutney its deep, roasted-tomato character. These compounds cannot form while water is present because water caps the temperature at 100°C. The brick-red colour indicates adequate Maillard compound formation.
Cool completely. Blend to smooth paste. Pour into bowl. Make tempering: pop mustard seeds in hot oil, fry urad dal golden, add curry leaves and hing. Pour over chutney and mix immediately.
The mustard seeds contain sinigrin — a glucosinolate that hydrolyses to allyl isothiocyanate when the seeds pop in hot oil, providing the sharp, horseradish-like pungency of South Indian tempering. This compound is volatile and must be captured by immediate mixing — delaying the mix allows it to vaporise into the air rather than infusing the chutney.