Dice potatoes into cubes and break cauliflower into florets.
Heat oil in a pan, temper cumin seeds, and sauté chopped onion with ginger paste.
Add chopped tomatoes, turmeric, red chili powder, and salt; cook until soft.
Add potatoes, cauliflower, and water; cover and simmer for 15 minutes until tender.
Serve warm with rotis.