Heat olive oil in skillet over medium heat. Put apple, sugar, lemon juice, and pepper flakes in skillet. Cook over medium heat until apple is tender and liquid is gone. Put aside.
Cook sausage and onion in skillet until brown. Drain grease and put aside.
Whisk eggs, half & half, salt, and a dash of black pepper together, until well blended.
Put sausage into pie shell. Top with apple mixture and cheese. Pour egg mixture over cheese. Sprinkle with parsley.
Bake uncovered 55 to 60 minutes at 375 degrees F, or until knife comes out clean. Let cool 10 minutes before slicing. Garnish with apple slices and parsley.