method
1. Cook the onions in a heavy-bottomed pan in the oil over low heat.
2. Shake the pan so that the onions are browned on all sides.
3. Add the port or vermouth and the vinegar and bring to the boil.
4. Reduce the heat and stir in the brown sugar, raisins, salt and cayenne pepper.
5. Cover and simmer for 15 - 20 minutes until the onions are tender and the liquid has reduced to a syrup.
6. Serve the onions hot with their syrup.
