Heat olive oil in a large pan.

Add sliced red onions, bay leaf, and thyme to the pan.

Season with salt and freshly ground black pepper.

Cover the pan with a lid and cook over low heat, stirring occasionally, for 30 minutes, or until onions are softened but not colored.

Stir in demerara sugar, balsamic vinegar, red wine, and orange zest and juice.

Cook uncovered for 1 hour and 30 minutes, until no liquid remains and the onions are a dark, rich red color.

Stir frequently during the last half hour to prevent burning.

Cool the mixture completely.

Transfer to sterilized jars.

Store in the refrigerator until needed.