Red onions contain vitamin C, fiber, and calcium. Sweetness is the red onion’s greatest strength. A milder and sweeter onion, often consumed raw in salads or can be lightly cooked with other foods. Storage tips: Place them in a well-ventilated cool dark place: between 40-50f (4-10c). Once it is peeled it is best stored in the fridge to avoid contamination. Sliced or chopped raw onions should be stored in airtight containers and refrigerated.