In a 10-inch oven safe pan, saute the first three ingredients until the onions are translucent and the mushrooms cooked. Add in the garlic and spinach; cook until the spinach has wilted. Add the asparagus and warm it up in the skillet with the other ingredients.
In a small bowl, whisk the eggs, egg whites, pizza sauce, oregano, salt and pepper together.
Pour over the vegetables in the skillet, stirring if needed to disperse the vegetables evenly.
Place the tomato slices on top.
Place in the 350-degree oven and bake for 20-22 minutes, until the egg is fully cooked in the middle of the skillet. Sprinkle the mozzarella cheese on top and cook another 2-3 minutes until the cheese has melted.
Remove from the oven and serve, using salt and pepper to taste.
Adjust the quantities as desired. You can also sub in other vegetables if you want!