This yogurt condiment is served with Southern Indian Chicken Curry with Mustard Seeds.
Grate enough cucumber on the large holes of a box grater to measure 1/2 cup. Transfer to a clean kitchen towel, and squeeze out as much liquid as possible.
Stir together cucumber, yogurt, and salt in a small bowl. Stir before using, and sprinkle with chili powder.
Refrigerate in an airtight container up to 1 day.