Preheat your oven to 375°F (190°C).
In a 10-inch oven-safe skillet, cook the bacon slices over medium heat until they reach your desired level of crispiness.
Remove the bacon from the pan, let it cool on a paper towel, and then chop it into small pieces.
Discard all but one teaspoon of the bacon fat from the skillet and add the avocado oil.
Add the diced yellow onion to the skillet and sauté for 3-4 minutes until translucent and soft.
Add the baby spinach to the pan and stir until it is just wilted, then spread the vegetables evenly across the bottom.
In a medium mixing bowl, whisk together the large eggs, liquid egg whites, sea salt, and black pepper until the mixture is frothy.
Pour the egg mixture into the skillet over the spinach and onions, then sprinkle the chopped bacon and shredded cheddar cheese over the top.
Transfer the skillet to the oven and bake for 12 to 15 minutes, or until the eggs are completely set in the middle and the edges are lightly browned.