In a bowl, whisk together eggs and milk. Stir in onion, pepper, salt and pepper.
Spray a small nonstick skillet with cooking spray and heat over medium low heat. Pour egg mixture into skillet and as egg begins to set, use a spatula to gently push cooked portions to the centre. Tilt pan to allow uncooked eggs to flow into empty spaces.
Sprinkle with cheese and cook for 1 minute or until eggs are set and cheese is melted.
Divide egg in two and place each half onto a tortilla. Roll up to enjoy.