Remove any outer damaged leaves and cut the cabbage into quarters. Cut away the hard stalk and shred the cabbage finely. Peel and finely chop the onion.
Melt the fat in a heavy saucepan. Sprinkle in the sugar and heat steadily until the sugar melts and just begins to turn golden brown. Immediately add the roughly chopped tomatoes with the juice from the can and the onions and cook for a