Heat the vegetable oil in a large pot over medium heat. Stir in the cumin and ground red chilies, and cook for a few seconds until the spices are fragrant. Add the serrano chiles, onions, garbanzo beans, lemon juice, and water; season to taste with salt. Bring to a boil over high heat, then reduce heat to medium-low, and simmer until the vegetables are tender and most of the liquid has evaporated, about 15 minutes. Sprinkle with ginger, tomatoes, and cilantro to serve.