In a bowl, whisk together the eggs, water, and salt until well combined.

Heat a 9-inch sauté pan (such as a cast iron skillet) over medium heat. Grease with butter or oil.

Pour the whisked eggs into the pan, tilting it slightly to evenly coat the bottom.

Place both slices of bread into the eggs, pressing gently to soak both sides. Let them sit in the pan as the eggs cook.

Once the eggs are fully set, carefully flip everything over so the bread is now on the bottom. Layer on the sliced avocado and cheddar cheese.

Fold the edges of the egg in toward the center, then fold the sandwich in half. Cook for another 1-2 minutes per side, until golden brown and the cheese is melted.