There is really no recipe for kachumber. Its a relish made with onions, tomato and in our home, some cucumber and yogurt. A little bit of salt and cumin powder finishes it

I use half an onion, half a tomato, one fourth of a cucumber with 2-3 table spoons of yogurt. Add a pinch of salt and cumin powder. Its a refreshing raw relish with spicy curries.