In a medium mixing bowl, whisk together the eggs, egg whites, Greek yogurt, sea salt, black pepper, and garlic powder until the mixture is completely smooth and combined.
Place a non-stick skillet over medium heat and add the extra virgin olive oil, swirling to coat the pan.
Add the fresh spinach to the skillet and sauté for 1-2 minutes until the leaves are just wilted.
Reduce the heat to medium-low and pour the egg mixture into the skillet over the spinach.
Using a silicone spatula, gently push the eggs from the edges toward the center, allowing soft curds to form slowly.
When the eggs are about 80% cooked and still look slightly wet, sprinkle the crumbled feta cheese over the top.
Fold the feta into the eggs gently for another 30 seconds until the eggs are set but still creamy.
Toast the sourdough bread until golden and crisp.
Transfer the scramble to a plate and serve immediately with the warm sourdough toast.