HEAT oil in large skillet over medium-high heat. Add onion; cook, stirring frequently, for 1 to 2 minutes. Add squash; season with salt. Add water; reduce heat to medium. Cook, stirring occasionally, for 5 minutes or until squash is soft.
PREPARE pasta according to package directions, reserving 2 tablespoons cooking water.
MELT butter in medium skillet over medium heat. Add pasta, 2 tablespoons cheese and reserved cooking water; cook for 2 minutes.
SPREAD butternut cream on serving plates. Top with pasta; sprinkle with sunflower seeds and remaining 2 tablespoons cheese.