Preheat the oven to 400 °F, and grease or oil a 9 inch pie dish. In a large mixing bowl combine: 5 beaten eggs, ½ cup egg whites, ½ cup ricotta, ½ teaspoon sea salt, ¼ teaspoon ground mustard, and ¼ teaspoon black pepper. Whisk and beat all ingredients together. Make sure to break up the ricotta well. It is okay if there are small ricotta clumps.
Add spinach, and crumbled bacon to the egg mixture and stir in. Pour the egg mixture into the prepared pie dish. Place tomato slices on top of the frittata. Bake for 30 minutes or until the center is done and no longer liquid.
Remove frittata from oven and sprinkle with optional grated cheese. Cool and serve.
Notes
Nutritional Data includes the ½ cup grated cheese.*all nutritional data are estimates based on the products I used.*