01 - Whisk together eggs, milk, salt, pepper, and Italian herbs in a medium bowl until completely smooth and uniform in color.
02 - Fold cherry tomatoes, spinach, bell pepper, onion, zucchini, and cheese (if using) into the egg mixture until evenly distributed.
03 - Preheat the air fryer to 350°F for 3 minutes to ensure even cooking from the start.
04 - Brush a 7-inch round, oven-safe pan or cake tin thoroughly with olive oil to prevent sticking.
05 - Pour the egg and vegetable mixture into the prepared pan, place in the air fryer basket, and cook at 350°F for 12–15 minutes until the center is set and top is lightly golden.
06 - Let the frittata cool for 2 minutes to allow it to set properly, then slice into wedges and serve warm.