Preheat the broiler. Whisk 1/2 tsp. salt and pepper in a medium bowl and set aside. Heat the oil and butter in a 9-1/2 inch diameter nonstick ovenproof skillet over medium heat. Add the asparagus and sauté until crisp-tender, about 2 minutes. Raise the heat to medium-high. Add the tomato and a pinch of salt and sauté 2 minutes longer. Pour the egg mixture over the asparagus mixture and cook for a few minutes until the eggs start to set. Sprinkle with cheese. Reduce heat to medium-low and cook until the frittata is almost set but the top is still runny, about 2 minutes. Place the skillet under the broiler. Broil until the top is set and golden brown on top, about 5 minutes. Let the frittata stand 2 minutes. Run a rubber spatula between the sides of the frittata and the skillet to loosen and slide onto a plate. Serve and enjoy.