Red onion is a type of onion with purplish-red skin and a mild to sweet flavor. It is a versatile vegetable used in various cuisines. It has a deep purple or reddish skin that is thin and papery. When sliced, the inner layers reveal a reddish-white or pinkish hue. They have a rounded shape with multiple layers. Red onion has a mild to sweet flavor compared to other onion varieties. They are less pungent and have a milder onion taste.