Preheat broiler. Snap off and discard the tough ends of the asparagus. Cut the spears diagonally into 1 inch lengths. Set aside. Place the oil in a 10 inch ovenproof skillet set over medium high heat. When the oil is hot but not smoking add the onion and sprinkle with salt. Lower the heat to medium-low and cook, stirring occasionally, until the onions are softened but not browned, about 2-3 minutes.

Add the asparagus to the skillet and reduce the heat to low, Cover and cook for about 5-6 minutes, or until the asparagus is barely tender. Pour the beaten eggs into the skillet and leave over the heat for another 2 minutes or until the eggs are almost set but still runny on top.

Sprinkle the cheese evenly over the eggs. Remove the skillet from the top of the stove and transfer to a rack set about 4 inches below the broiler. Watch closely! Broil only until the cheese is melted and brown, about 2 minutes depending upon the broiler. Run a spatula around the edge of the frittata to loosen it from the pan and carefully slide it onto a large serving platter. Let it sit for 2 minutes, then cut into wedges. Serve hot or at room temperature. (224 calories/serving; GL=0, Glycals=1)