Kale Frittata - A Healthy Breakfast Casserole

large organic eggs

freshly grated Pecorino Romano or Parmesan cheese, divided

coarse kosher salt

freshly ground black pepper

extra-virgin olive oil

medium onion, thinly sliced

bunch organic Kale or Red chard (about 10 ounces), stems and center ribs cut away, leaves coarsely chopped

pepperoni or thinly sliced Italian spicy salami, cut into ½-inch pieces (about ⅔ cup)

garlic clove, minced