Start by preheating your air fryer to 300°F (150°C). This is an important step that ensures your eggs cook evenly.
In a mixing bowl, crack the eggs and whisk them together until well combined. Feel free to add a splash of milk or cream for creaminess!
Stir in the diced bell peppers (and onions, if using), cheese, salt, and pepper. Mix until all ingredients are evenly distributed.
Lightly coat your air fryer basket with non-stick cooking spray or a small drizzle of olive oil to prevent sticking.
Pour the egg mixture into the air fryer basket, spreading it evenly.
Set the timer for 10 minutes and cook. At the halfway mark, give the basket a little shake to ensure even cooking.
After 10 minutes, check the eggs; they should be set and slightly golden on top. If they need a little more time, add another minute or two as necessary.
Once done, remove the basket and let it cool for a moment. Slice into squares, and it's ready to serve!