In a medium-sized bowl, add the eggs, milk, and everything seasoning together with a tiny pinch of salt.
Then grease an 8-inch non-stick pan, heat on low to medium heat. Then add the whisked eggs, spinach leaves, and cheese over top. Let the eggs cook through on the bottom (about 2 minutes).
Add the avocado on top, then use a rubber spatula or regular spatula to flip the one side over. Hold the spatula there for a few seconds to help the omelette form. Let cook for 2 minutes.
Then carefully flip the omelette and let it cook for another 2 minutes, or until the eggs are solid to touch and the inside is no longer wet (you can check with a fork). Cover with a lid if needed to trap the heat so the inside thoroughly cooks. Serve and enjoy!
What to serve on the side - add even more flavor by topping your omelette with fresh basil or cilantro, and serving it with a dressing like salsa or ketchup! You can also serve it alongside some whole-grain toast and fresh fruit.