In a Dutch oven or 4-quart sauté pan with a lid, heat the oil over medium-high heat. Once warm, add the cumin and turmeric. Cook until the seeds sizzle and turn reddish-brown, about 40 seconds.
Add the onion and pinch of salt. Cook 2 to 4 minutes, until the onions brown slightly, stirring occasionally.
Add the ginger and garlic. Cook another minute or less, stirring occasionally.
Add the potato and jalapeño, if using, and cook 1 to 2 minutes, until the potato softens slightly.
Add the cauliflower, garam masala, coriander, and 1 teaspoon salt. Mix well until all the florets are yellow from the turmeric. Cook about 2 minutes and then add the tomatoes and water.
Cover the pan, turn the heat down to medium-low, and cook for 20 to 25 minutes, or until the vegetables are soft, stirring occasionally. Cook a little less if you want a tiny bit of crunch, and cook a little longer if you want the vegetables to be a little softer. Add up to ½ cup additional water if the vegetable mixture is too thick.
Remove from the heat, add the cilantro, and put the lid back on. Let the aloo gobi sit for 3 to 5 minutes before serving to help the flavors all come together. Serve with roti, naan, or basmati rice.