Heat oven to 375 degrees F. Coat an 8-inch square baking dish with no-stick cooking spray.
Heat oil in large saucepan over medium heat. Add onion; cook 5 minutes or until tender, stirring occasionally. Add gingerroot and garlic; cook 1 minute. Add tomato sauce, water, peanut butter, cumin and coriander; stir until smooth. Cook 2 minutes or until thickened, stirring constantly.
Add sweet potatoes to saucepan. Mash with potato masher until mixture is well blended. Spoon into prepared baking dish. Bake 25 to 30 minutes or until heated through. Garnish with chopped cilantro.