Out of onions? Use 1 tablespoon onion powder for 1 small onion. It replaces the flavor, not the texture, so it suits soups, sauces and rubs.
1 small onion = 1 tbsp onion powder (flavor only)
Good for soups, sauces and dry rubs. Stir it into the sauce or liquid. It replaces the onion flavor, not the bulk, moisture or texture, so skip it for dishes built on onion pieces.