Cover Onion Skins, half pounds worth if you can get them, with water.
Bring to a simmer for about 15 minutes and then allow to sit overnight - doing this allows the dye molecules to leach from the onion skins.
Next day bring to a simmer and let simmer for about an hour before adding pre-mordant fabrics, fibers, etc.
Allow the fibers to simmer for an hour do NOT bring to a boil as this will bring out the browns in the dye molecules and you don't want that.
Shut off the heat leaving the fabircs in the dye bath.
Allow the dyebath and fabric to sit overnight.
This has yeilded the best color to date that has been quite lightfast.