Preheat your oven to 375°F (190°C).
In a medium bowl, whisk together the egg whites, whole eggs, sea salt, and black pepper until well combined.
Heat the olive oil in a 10-inch oven-safe skillet over medium heat.
Add the diced red onion and bell pepper to the skillet, sautéing for about 5 minutes until the vegetables are tender.
Stir in the minced garlic and halved cherry tomatoes, cooking for an additional 2 minutes until fragrant.
Pour the egg mixture over the vegetables in the skillet, ensuring they are evenly distributed.
Sprinkle the crumbled feta cheese over the top of the eggs.
Transfer the skillet to the preheated oven and bake for 12-15 minutes, or until the eggs are set and the top is lightly golden.
Remove from the oven, garnish with fresh parsley, and slice into wedges to serve.