1. Place the onions in a large saucepan with the salt and water and stir.
2. Put a plate on top to keep the onions under the brine.
3. Leave for 12 hours.
4. Peel the onions carefully and return to the brine for a further 24-36 hours.
5. Meanwhile, to make up the spiced vinegar, dissolve the sugar in the vinegar over a low heat, stir in the spice, bring slowly to the boil and boil for a few seconds.
6. Leave with the spices to become cold.
7. Drain the onions well and pack into jars suitable for vinegar and pickles.
8. Strain the vinegar and pour over the onions. Cover and seal. Leave for 3-4 months before eating.