Use a blender to grind the ginger, 1 teaspoon cumin, and green chile peppers.
In a medium saucepan, add 1 cup water, pineapple, tomato, and salt. Place over a low heat. When the pineapple and water have come to boil, add the ground mixture. Raise and lower the heat to bring to a boil several times. Add the remaining water, and bring to a boil again. Add cilantro, and remove from heat. Mix in lime juice.
In a small pan, heat oil over medium heat, and add the remaining cumin seeds. Fry till golden, and add to the soup as a garnish.