Preheat your oven to 375°F and lightly grease a small oven-safe baking dish with a touch of olive oil.
Heat the olive oil in a skillet over medium heat and add the diced sweet potatoes and onions, sautéing until the potatoes are tender and the onions are translucent.
Add the ground turkey sausage to the skillet, breaking it apart with a wooden spoon and cooking until it is browned and cooked through.
Toss in the fresh spinach and stir for 1 minute until it is just wilted, then remove the skillet from the heat.
In a mixing bowl, whisk together the large eggs, egg whites, sea salt, black pepper, and garlic powder until the mixture is light and airy.
Transfer the sausage and vegetable mixture into the prepared baking dish, spreading it out into an even layer.
Pour the egg mixture over the vegetables and sausage, then sprinkle the crumbled feta cheese evenly across the top.
Bake for 20 to 25 minutes until the eggs are fully set in the center and the edges are slightly golden.