In a separate bowl, combine eggs and egg whites. Beat lightly until eggs are fully combined. Stir spinach, artichoke hearts, onions and half of the cheese into the egg mixture until all ingredients are blended.
Pour egg mixture into a 10" cast iron skillet coated with olive oil or PAM spray (I used PAM spray to cut down on the oil and keep the recipe a little bit lighter).
Place skillet on stovetop over medium high heat and cook until the bottom of the frittata has set but the top is still jiggly. Top with remaining parmesan cheese. Place in oven, and bake for about 20-25 minute or until frittata is set and begins to brown.
Recipe by In Good Taste at https://ingoodtaste.kitchen/spinach-artichoke-frittata/