Heat a large skillet over medium heat, melt butter and add onions.
Heat oven to 350°F. Spray pie dish with non stick spray. Set aside.
Caramelize onions by stirring every few minutes. If they start burning, turn down the heat and stir more often. Keep cooking until soft and golden. About 20 minutes.
In a medium bowl, whisk eggs, spices, ½ the cheese and heavy cream.
Place onions in the bottom of the pie dish. Pour egg mixture on top.
Add remaining cheese around the outer edge of the pie dish. If you put it in the middle, it'll keep the quiche from rising in the center.
Bake on center rack for 30-35 minutes or until center is just set.
Allow to cool 5 minutes, then dish and serve. Top it off with fresh arugula and watered down sour cream (so it drizzles, rather than dollops).