Onion powder is a seasoning made from dehydrated ground onions.oss it into spice rubs and spice blends, dressings, dips, frying batter mixes, sauces, soups, stews, salads, sauces, curries.Onion Powder is a light, shaded, fresh off-white with a red undertone.Onion powder provides a similar flavor of fresh onions with a concentrated flavor profile and nutrient content.