Preheat oven to 400 degrees.
In a medium metal sauce pan on low heat, toast one half cup black walnuts. Remove black walnuts from heat, cool and chop cooled black walnuts.
Separate twelve egg whites to a large glass mixing bowl. Thinly slice one half cup red onion and separate into rings. Slice one large granny smith apple. Remove stems from one cup flat parsley. Cube one cup raclette cheese.
Warm two tablespoons green onion infused oil in a large metal skillet over medium heat. Lay half of the onion rings on the bottom of the skillet and cook for two minutes. Gently pour in egg whites on top of the onion rings. Layer on half the apple slices, half the flat parsley and half the raclette cheese.
Cook frittata on medium heat uncovered for five minutes until the eggs begin to set. Layer on the remaining onion rings, apple slices and flat parsley. Transfer frittata to the oven and bake uncovered in the over for ten minutes.
Remove frittata from oven and add remaining raclette cheese, toasted black walnuts and bake for five additional minutes. Remove frittata from oven and let rest for five minutes. Plate each frittata serving with one tablespoon of hard apple butter.