How to Make It
Place onion in a medium bowl and add lime juice.
Using a vegetable peeler, peel mangoes; discard peel. Carefully shave mangoes top to bottom to create long, thin ribbons.
Place mango ribbons in bowl with onion, and add chile, salt, and pepper. Toss to coat. Add 1 tablespoon sugar, and toss again. Taste for sweetness and add additional sugar to taste. Cover and chill for at least 2 hours and up to 2 days.