Place onions and olive oil in a large saucepan and cook until golden. Then add asparagus and cook for 5-8 minutes. Place cover on saucepan while asparagus is cooking and mix every minute or two. Then add tomatoes and cook for another 5 minutes. Continue to mix all ingredients every one to two minutes. Then, add potatoes and any additional seasoning you desire, and cook for another couple minutes. Next, add egg whites and make sure it is well distributed in your saucepan. Place cover on saucepan and lower heat to a simmer. Cook for about five to eight minutes. Check to make sure eggs are cooked then serve.