Heat the oil in a pan on a medium-to-low heat and add the cumin seeds. Once they begin to sizzle, add the garlic and cook for a minute, until it is just beginning to color. Add the onions and cook for 2 minutes so that they begin to soften. Now turn the heat to high, add the potato and cook for 2 minutes.
Add the salt, garam masala, chile powder and chaat masala, plus the tomato and okra. Cover and cook for 10 minutes on a low heat, until the vegetables are tender.
Remove the lid and finish on a high heat for 2 minutes, to crisp the vegetables slightly. Stir in the lemon juice and serve. Do ahead: This will keep in an airtight container in the fridge for 4–5 days. Reheat thoroughly before serving.
