Preheat oven to 425 degrees Fahrenheit.
While oven preheats, wash and peel sweet potato. Slice into approximately ¼ inch pieces.
Toss sweet potato in olive oil and line bottom of baking dish with sweet potato.
Bake crust for 20 minutes or until sweet potato feels tender. Turn oven down to 350 degrees Fahrenheit.
Quickly saute onions and spinach on the stove top.
Top sweet potato crust with onions, feta, spinach, cranberries, salt and pepper.
In a large bowl, whisk together eggs and pour over dish.
Place quiche back in oven for 25 minutes or until egg cooked through.
Allow to cool and serve!