Fry onion in a wide shallow cooking pot until it starts browning.
Add the caster sugar to the same pot, stir a few times to help the sugar dissolve.
Stir in cabbage, wine, water, ½ of the vinegar, caraway seeds and salt. Cook for 30 minutes with the lid on.
Pre-mix flour with a small amount of fairly warm (not boiling) water into smooth, pourable consistency.
Turn the heat down and pour the flour in. Stir continuously to incorporate the flour into the braised cabbage to prevent lumps.
Cook for an additional 3 - 5 minutes. Stir occasionally.
Adjust the taste by adding a splash of the remaining vinegar at a time. Taste in between to make sure you adjust the flavours according to your taste buds. Season with more salt if needed.