Heat a non-stick skillet over medium heat and cook the turkey bacon until crisp on both sides.
Remove the bacon from the pan, chop it into bite-sized pieces, and set it aside.
In the same skillet, lightly sauté the fresh spinach until just wilted, then remove and set aside.
Wipe the skillet clean and add the avocado oil, ensuring the surface is evenly coated.
Whisk the egg whites briefly and pour them into the hot skillet, cooking until the edges are set and the bottom is golden.
Layer the sautéed spinach, crispy turkey bacon, and feta cheese onto one half of the omelet.
Carefully fold the omelet over the filling and cook for an additional minute to ensure the cheese is slightly softened.
Slide the omelet onto a plate and garnish with fresh avocado slices and a pinch of black pepper.