In a medium bowl, whisk the eggs whites, 1/2 a teaspoon of sea salt, and ground pepper until frothy.
Heat the avocado oil in a large skillet over medium-high heat.
Add the onion, bell pepper, and 1/2 a teaspoon of sea salt and sauté until slightly softened, about 3 minutes.
Add the zucchini and the garlic and sauté until slightly softened, about 3 more minutes.
Pour the egg white mixture over the veggies and tilt the pan, allowing the eggs to spread to every corner.
Turn the heat to low.
Cover and cook for 3-5 minutes or until the egg whites are no longer translucent.
Remove the lid and flip the omelet. You can use two spatulas to make things easier. Alternatively, you can place a large plate board over the skillet and invert the omelet onto the plate before sliding it back into the pan.
Cook for another minute.
Cover half of the eggs in the bacon and grated parmesan, if you're using them.
Fold the omelet over the cheese and bacon to create a half-moon shape
Cover, turn the heat off, and let sit for 1-2 minutes or until the cheese has melted. If you choose not to add bacon or parmesan, you can skip this step and serve right away.
Cut in half and serve.
Store leftovers in an airtight container in the fridge for up to 3 days.
Reheat in the microwave on 80% power in 15-second increments until heated all the way through.