Heat a small skillet over medium high heat and cook the peppers, onions, and broccoli until slightly softened, about 5 minutes. While the vegetables are cooking, whisk together the egg with the egg whites and season with salt and pepper. (Note: you can just use 2-3 whole eggs instead if you prefer).
Pour the eggs over the vegetables and stir for a minute to partially cook the eggs, then spread the top smooth with a spatula. Sprinkle the top with the cheese and place on a middle to lower rack in the oven under the hot broiler. Cook until the eggs are set, about 3-5 minutes, watching carefully so that the top doesn't burn.
Recipe by Cooking With MicheleĀ® at https://cookingwithmichele.com/2014/08/lunch-one-vegetable-frittata/