Add cumin powder, black salt and regular salt and mix well.
Add green chilli, cilantro, onion and tomato and mix well.
Add little milk if it is too thick.
Refrigerate it for a few hours before serving.
Notes
Yogurt - Use plain yogurt to make the raita. You can later flavor it according to your preference. Greek Yogurt can be used if don't have plain yogurt.Salt - Add salt just before serving the raita. If you add it earlier, the veggies will leave some water the raita will get thinner.