Traditionalists who like their cauliflower smothered in a rich cheese sauce may be surprised to see it roasted. The roasting process seems to bring out a nutty flavour, which makes a winning combination with the sweet and sour caper topping.
Heat the butter in a small frying pan, add the vinegar and sugar and caramelise lightly together. Stir in the capers, sultanas and water and heat through, bubbling for a few minutes if necessary to reduce to a glaze. Season with salt and pepper.
Put the cauliflower in a serving dish and pour over the sweet and sour capers and sultanas.