Preheat the oven to 350 degrees F.
Spray a 12-cup muffin tin with cooking spray, and set aside. In a saucepan, heat oil over medium heat and then add chopped tomatoes, onion, salt and pepper. Saute approximately 5 until lightly browned and tender. Remove from heat and allow to cool for a few minutes.
While the veggies are cooking, whisk egg whites, whole eggs, cheese, yogurt, flour, and basil into a mixing bowl. Whisk until ingredients are well blended. Set aside.
Once the veggie mixture is cooled, add to the mixing bowl with the egg mixture and stir with a spatula until all ingredients are well blended.
Spoon the egg mixture into each of the 12 muffin cups.
Place in oven and cook for approximately 15 minutes, or until cooked through and browned on top. Let cool for 5 minutes before serving.