Steps

1. Heat the oil in a wide pot over medium-high heat.
2. Add the mustard seeds, stirring constantly. When the seeds begin to change color and pop (about 30 seconds), add turmeric, garlic, ginger and optional cayenne. Stir briefly, add onions, lower heat to medium and cook until onions are soft, about 5 minutes.
3. Add tomatoes and cook for until the tomatoes soften, then add cauliflower and potatoes. Stir everything together, turn heat to medium low, cover and cook until potatoes and cauliflower are soft, stirring occasionally. If vegetables appear too dry or start to stick to pot, add up to ½ cup of water. When vegetables are soft, add masala, stir together and cook for 1 minute. Taste, adjust seasonings, salt to taste, add cilantro and serve.