Mix the coriander, cumin, chili/cayenne and turmeric powders in 2 Tablespoons water and add the mix to the pan. Cook for a 1 minute or so until the spices get fragrant and leave oil on the side. Add potatoes, cover and cook for 2 minutes. Add cauliflower and cover. Cover and cook potatoes and cauliflower on low heat for 10-15 minutes until the veggies are just about getting tender. Stir every 5 minutes.