1. Spray a medium skillet with cooking spray and heat over medium-high heat. Add peppers and cook until tender. Add spinach and cook until wilted. Season with salt and pepper.

2. In a medium bowl, whisk egg whites together. Add to skillet and stir to combine. Continue cooking, incorporating runny parts with more cooked parts. Using a heatproof rubber spatula, push together any holes that may have formed; season with salt and pepper.

3. Run spatula along right side of omelet to loosen egg whites from skillet. Place spatula under right side of eggs, making sure that the spatula is well underneath the eggs to offer maximum support, and lift right side over in one fluid motion. Folded omelet should look like a half-moon.

4. Lift up skillet with one hand, and hold a plate with your other hand. Tilt skillet, and let the curved edge of the omelet slide onto the plate. Serve immediately.