"Use up leftover cooked greens (which, in my experience, don't reheat so nicely) in this delicious frittata! You can use spinach, Swiss chard, kale, etc."
1Preheat the oven's broiler and set the oven rack in the upper third of the oven. Beat the eggs and egg whites in a mixing bowl until smooth. Whisk in the parsley, 1/4 teaspoon salt, and 1/4 teaspoon pepper until evenly blended; set aside.
2Heat the olive oil in a 10-inch cast-iron skillet over medium heat. Stir in the onion, and season with 1/4 teaspoon salt, and 1/4 teaspoon pepper. Cook and stir until the onion softens and turns translucent, about 5 minutes. Stir in the tomatoes, and cook an additional minute. Add the cooked Swiss chard; cook and stir until the Swiss chard is hot. Pour in the egg mixture, cover, and cook until the edges of the egg have set, about 5 minutes.
3Uncover the frittata, and sprinkle with Parmesan cheese. Broil in the preheated oven until the cheese is golden brown and the center of the frittata has set, about 2 minutes. Remove from the oven, and let stand 3 minutes before serving.
Footnotes
Tip
Aluminum foil helps keep food moist, ensures it cooks evenly, keeps leftovers fresh, and makes clean-up easy.