A splash of vinegar keeps red cabbage red

Half a red cabbage on the board is one of the prettiest things in a November kitchen: deep purple outside, white veins running through it like marble. The knife crunches through it, the leaves squeak, and my fingers turn lilac straight away. The first time I braised one, though, it came out of the pan blue. A sad, greyish blue, even though it tasted perfectly fine. I served it anyway and nobody said a word, but I knew.

It turned out the cabbage needed something sharp. Red cabbage changes colour a bit like litmus paper: the purple colour in its leaves drifts towards blue when the pan is not acidic enough, and stays ruby when there is a little acid in it. Hard tap water can push it towards blue too. So the sharp things go in at the start, not as an afterthought: a grated tart apple and a tablespoon of cider or wine vinegar. That small spoonful is the whole trick.

Here is how I braise it. I take out the hard core, slice the cabbage thinly and put it in a colander. In a wide heavy pan I warm a tablespoon of oil or a knob of butter and soften a thinly sliced onion for about eight minutes, until it is sweet and golden at the edges. Then the cabbage goes in, with the grated apple, the vinegar, a pinch of salt, a spoonful of brown sugar if the apple is very sharp, and a splash of water, about 100 ml. Sometimes a bay leaf or two cloves, if I feel like something warmer. I stir it all round, put the lid on and turn the heat right down.

Then I leave it for about an hour, stirring every quarter of an hour or so. I check that the bottom of the pan isn't dry; if it is, another splash of water goes in. The cabbage collapses slowly, from a big bright heap into a soft, glossy pile half the size. The kitchen smells of apple, onion and something sweet and sour, a smell that, for me, means the evenings are getting dark early.

At the end I taste it. If it is too sweet, a drop more vinegar; if it is too sharp, a pinch of sugar. Vinegar added at the end brightens the colour almost at once, which always feels like a little magic. I take out the bay leaf and the cloves, because nobody wants to bite a clove.

There is always more than one supper's worth, which is no bad thing, because braised red cabbage is even better the next day. But leftovers need looking after. I spread what is left in a shallow tub so it cools faster, and once it has cooled I get it into the fridge within two hours of cooking. My fridge runs at 5°C or below. We finish it within two days. If I can see we won't, a portion goes into a tub in the freezer the same day, labelled with the date. It defrosts overnight in the fridge.

When I reheat it, I only warm up what we'll eat at that meal, and I heat it until it is steaming hot all the way through, stirring so the middle isn't cold. I reheat it once, not over and over. Whatever comes back to the table a second time stays there.

With sausages, with a roast chicken, with plain boiled potatoes and a spoonful of soured cream, it dresses up an ordinary weekday plate, no occasion needed. It goes on toast with a bit of cheese, too. Just don't forget the spoonful of something sharp.

Braised red cabbage with apple. Serves 4–6. About 1 hour 15 minutes. You need half a medium red cabbage (about 700 g), 1 onion, 1 tart apple, 1 tbsp cider or wine vinegar, 1 tbsp oil or butter, 1 tbsp brown sugar (optional), salt, 100 ml water, a bay leaf or 2 cloves (optional). Core and thinly slice the cabbage. Soften the onion in the oil for 8 minutes. Add the cabbage, grated apple, vinegar, sugar, salt and water. Cover and cook on a low heat for about an hour, stirring now and then and adding water if the pan dries. Season to taste with more vinegar or sugar. Cool, then chill within 2 hours; eat within 2 days or freeze. Reheat once until steaming hot.