Heat a wide stir fry pan and add oil when it is hot. Once the oil is hot, add cumin seeds and let them sizzle. Then add chopped garlic, broken red chili, curry leaves, asafoetida, and turmeric and saute for a few seconds.
Then add sliced onions and ¼ teaspoon of salt to help onions cook faster. Saute onions for 2 or 3 minutes just until they are a little translucent.
Then add coriander powder, cumin powder, and stir well. Saute the spice powders with onions for a minute.
Now add potato cubes,1 teaspoon of salt, and mix well. Cover the pan with a lid and cook until the potatoes are almost done while stirring every couple of minutes to avoid burning. If required, you can add 1 to 2 tablespoons of water while the potatoes are cooking.
When the potatoes are almost cooked, add chopped spinach, mix well and cook uncovered for around 3 to 4 minutes until the spinach and potatoes are well done but not overcooked.
Check the seasonings and add more salt or spices if needed. Also, add ¼ teaspoon of garam masala if you prefer.
Garnish with cilantro and serve hot with rice, roti or naan, and plain yogurt on the side.