Cheese & Asparagus Frittata

1. Snap the tough ends off of the asparagus and diagonally cut the spears into 1" lengths. Cut the onion into thin slices. 2. Heat olive oil in a 10" oven-proof frying pan over medium-high heat. Add onions and salt and cook, stirring occasionally, until onions are softened, about 3 minutes. 3. Add asparagus, reduce heat to medium-low, and cook, covered, until asparagus is barely tender, 6 to 8 minutes. 4. Lightly beat and add the eggs; cook until almost set, but still runny on top, about 2 minutes; pre-heat the broiler while the eggs cook. 5. Sprinkle cheese over eggs and place the pan in the oven; broil until the cheese is melted and lightly browned - 3 to 4 minutes. 6. Remove from oven and slide the frittata onto a serving plate. 7. Cut into wedges and serve immediately.