Grind coriander seeds, cumin and peppercorns to a fine powder.
Heat 3tbsp oil in a saucepan over medium heat, add the mustard seeds, curry leaves and dry red chili. Once the seeds start to splutter, add the garlic and onion. Cook for 2-3 minutes.
Add the ground spices, red chili powder and salt. Cook for another 2 minutes.
Next add the chopped tomato, tomato paste, vinegar and ½cup of water. Reduce the heat to low and cook, stirring occasionally, about 10-15 minutes.
Chutney is ready when it becomes thick and fragrant and is reduced to about 1 cup. Serve hot or cold.