Grease 9-inch glass pie plate. Combine hash browns with all but ⅛ cup of the onions and press mixture into pie plate to form crust. Sprinkle crust with pepper, Romano cheese, and garlic powder, then dot with spinach and feta cheese. Top evenly with cheddar cheese. Whisk together eggs and milk and pour over pie, working from edge to middle. Position reserved chopped onion on top of cheddar cheese in center of pie; sprinkle parsley in a ring around the onion then sprinkle paprika around parsley to make an outside ring. Refrigerate overnight.
In the morning: Bake at 325 degrees F until lightly browned, approximately 1 hour. Cool, cut into 6 slices. May be served with red salsa.