Preheat the oven to 180 degrees Celsius (350 degrees Fahrenheit) Gas 4.

Peel and finely grate the ginger. Combine all the plum sauce ingredients in a small saucepan over a low-medium heat, stirring occasionally, for 10–15 minutes until the sugar and spices have dissolved and you have a smooth sauce.

Arrange the cabbage slices, plums, and red onion on the prepared baking pans and drizzle evenly with the oil and then the sauce, reserving a little sauce to serve on the side of the dish.

Roast in the preheated oven for 25–30 minutes.

The cabbages should be browned and sticky but still have some bite when cooked. Serve with the reserved plum sauce on the side.