Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish.
Heat the extra virgin olive oil in a skillet over medium heat and add the diced onion and red bell pepper.
Sauté the vegetables for 3-4 minutes until they begin to soften and become fragrant.
Add the ground turkey sausage to the skillet, breaking it into small crumbles with a spatula, and cook until fully browned.
Stir in the fresh spinach and cook for 1 minute until just wilted, then remove the skillet from the heat.
In a separate mixing bowl, whisk together the eggs, egg whites, sea salt, black pepper, and garlic powder until well combined.
Spread the sausage and vegetable mixture evenly into the bottom of the prepared baking dish.
Pour the egg mixture over the top, sprinkle with crumbled feta cheese, and bake for 20-25 minutes until the center is set.