Preheat the oven to 375 degrees. Coat a round pie dish with olive oil cooking spray.
Layer thin slices of potato all over the edges and bottom of the pan, making sure to overlap them. Season the potatoes with sea salt and freshly cracked black pepper to taste. Coat the potatoes with olive cooking spray.
Place in the oven to bake for 20 minutes. Remove from oven and set aside.
Meanwhile, heat the butter or olive oil in a large skillet over medium heat. Add the onions and season with sea salt, and cook, stirring often, for 10 minutes, or until golden brown and tender.
Sprinkle caramelized onion, green chile, diced tomato, and cotija cheese over the potato crust.
Whisk the eggs with the milk and season with sea salt and freshly cracked pepper to taste.
Pour the egg mixture over the veggies and ham.
Place in the oven and bake for 30-40 minutes, or until a tester inserted in the center of the quiche comes out clean–don't overcook.
Remove from oven and let cool for a few minutes before slicing. Enjoy.