1Preheat oven to 400°F and spray a 9-inch pie dish with avocado oil spray.
2Place potatoes and 1 teaspoon of salt in a large pot, cover with cold water by 1 inch. Bring to a boil over medium-high heat and cook until fork tender (10-12 mins). Drain and immediately transfer to the pie dish.
3Press potatoes into and up the edges of the pie dish. Drizzle with avocado oil, season with remaining salt and pepper. Bake until golden and crisp (40-45 mins).
4Add spinach, cherry tomatoes, feta, olives, and shallots. Season with oregano and garlic powder.
5Whisk eggs and milk together, then pour over the potato crust and gently toss everything. Bake until eggs are set (30-35 mins).