Red onions are cultivars of the onion, and have purplish-red skin and white flesh tinged with red. They are most commonly used in cooking, but the skin has also been used as a dye.
Red onions tend to be medium to large in size and have a sweeter flavor than white or yellow onions due to low levels of pyruvic acid and sulfur compounds. They are often consumed raw (and can be added to salads for color and bite), grilled, or lightly cooked with other foods. Red onions are available throughout the year and are high in flavonoids and fiber (compared to white and yellow onions). Cut red onion can be soaked in cool water for a period of time, and the water can be drained off, resulting in less "bite" and pungency.