Red onions are sharp in flavour compared to the other common onions. Red Onions contain vitamin C, fibre, iron, and calcium. They also have a high polyphenol and flavonoid content, including a large amount of quercetin, which provides antioxidant properties that contribute to overall health, and sulfur, which promotes anti-inflammatory processes within the body. Most of the flavonoids which are known as antioxidants are concentrated more in the outer layers, so when you peel off the layers, you should remove as little as possible. Store in a cool, dry well-ventilated place.