Chop pepper and tomato into small pieces. Using an electric mixer or whisk, beat egg whites until frothy.
Set oven to broiler setting. Spray oven-safe skillet generously with cooking spray.
Place skillet on stove over medium heat. Add chopped peppers and cook for about 3 minutes, just until they begin to soften. Pour whipped egg over the peppers and cook for about 1 minute, gently moving the eggs around until the bottom begins to set. Sprinkle chopped tomatoes over the egg whites.
Place the skillet under the broiler. Broil for about 3 minutes or until the top of the frittata is lightly brown and just cooked through.
Using an oven mitt, remove the pan from the oven. Allow the frittata to cool for 4-5 minutes before attempting to slice and remove from pan. Serve with a green salad.