Cut cauliflower into flowerets. Cube potatoes. Heat oil and saute cumin seeds for about a minute. Add garlic and ginger, stir and add potatoes. Bhoona, add turmeric and chili powder, and bhoona again. Add tomatoes and simmer for about 5 minutes. Add cauliflower and high heat for about a minutes. Lower heat, cover and let simmer for about 15 minutes. Curry should be damp-dry.