In a medium skillet, heat olive oil. Add onions and cook a few minutes until softened. Add pork sausage and cook until browned. Drain any grease.
Line a pie plan with parchment paper. Fill with sausage mixture. Top with peppers. With a small spoon, place dollops of potatoes across the top.
In a small bowl, lightly beat eggs. Pour over other ingredients in pie pan. Top with liquid egg whites. Shake the pie pan lightly such that eggs fill throughout. Top with spinach
Bake for about 1 hour. You will want to shake the pan lightly to make sure the frittata does not jiggle too much.
Allow to sit for 5-10 minutes and then serve in triangle slices.