Preheat your oven to 375°F and lightly grease a small oven-safe baking dish with the avocado oil.
In a small non-stick skillet over medium heat, sauté the diced red onion and fresh spinach until the onion is translucent and the spinach is fully wilted.
Lay the turkey bacon slices across the bottom of the prepared baking dish and brush them with half of the maple syrup.
In a medium mixing bowl, whisk together the large eggs, egg whites, sea salt, and black pepper until the mixture is uniform and slightly frothy.
Stir the sautéed onion and spinach into the egg mixture, then pour the contents over the bacon in the baking dish.
Drizzle the remaining maple syrup over the top of the eggs for a caramelized finish.
Bake for 20 to 25 minutes, or until the center of the egg bake is firm and the edges are slightly golden brown.
Let the dish cool for 5 minutes before slicing and serving.