Ingredients:

1/2 cup thick, plain Curd or Yogurt
4 Tablespoons finely chopped Onions
a pinch of Salt (adjust to taste)
1 Tablespoon finely chopped Coriander leaves, for garnish
1 teaspoon Vegetable Oil
1 teaspoon Mustard Seeds
2 finely chopped Green Chili
1 Tablespoon fresh Curry Leaves
 
Method:

Whisk cold, thick, plain yogurt (curd / dahi) until smooth
Add finely chopped onions, salt to taste and mix well
Tempering / Tadka: Heat oil in a small pan, add mustard seeds and let them splutter, add green chili, curry leaves and fry for 10 seconds
Add the tadka to the onion and yogurt mixture
Mix well
Garnish with coriander leaves. Keep refrigerated until ready to serve
Consume within 1 day