Preheat your oven to 375°F and line a small square baking dish with parchment paper for easy removal.
Peel the sweet potato and dice it into small 1/2-inch cubes to ensure even cooking.
Place the sweet potato cubes in a steamer basket over boiling water for 6 minutes until just tender, then set aside.
In a non-stick skillet over medium heat, cook the ground turkey breast while breaking it into small crumbles until no longer pink.
Finely chop the fresh spinach and dice the red bell pepper into small pieces.
In a large mixing bowl, whisk together the egg whites, tamari, grated fresh ginger, garlic powder, onion powder, sea salt, and black pepper.
Gently fold the cooked turkey, steamed sweet potatoes, spinach, bell peppers, and sliced green onions into the egg white mixture.
Pour the combined mixture into the prepared baking dish and spread it into an even layer using a spatula.
Bake for 25 to 30 minutes or until the center is firm to the touch and the edges are lightly golden.