Preheat broiler. Melt butter in skillet over medium heat. Add green onions and sauté 1 minute. Add asparagus,sprinkle lightly with salt, and sauté until tender, about 4 minutes. Whisk eggs, 3/4 cup Fontina cheese, salt, and pepper in medium bowl. Add egg mixture to skillet; fold gently to combine. Cook until almost set. Slide into buttered 9x 13 inch baking sheet(use one with at least 1/2 inch sides) Sprinkle remaining 1/4 cup Fontina cheese and Parmesan cheese over. Broil until frittata is puffed and cheese begins to turn golden, about 3 minutes. Cut into small squares. Serve hot or rm. temp.