January is not a month most people associate with salad, but this is the exception. The blood oranges arrive in the market around the same time the cold properly sets in, and their colour alone is enough to justify the trip: that deep crimson bleeding into ruby, as if someone had stained them overnight. Next to a pile of watercress, dark and peppery and still damp, they look like they belong together. They do.

This is an old combination. The Victorians knew it, serving watercress with orange at winter tables when not much else was green and growing. I don't know whether they used blood oranges or navels, but I can tell you the blood oranges are worth waiting for. They bring a tartness that ordinary oranges don't quite have, and that colour against the dark watercress leaves is something you want on the table.

The dressing is barely a recipe. Juice from the orange trimmings, good olive oil, a flake of salt. The onion goes in thinly sliced and soaked for a few minutes in vinegared water, which tames the bite without killing it. That's it. No mustard, no honey, no garlic. The ingredients are good enough to carry the whole thing without interference.

I make this through the winter months whenever the blood oranges look right at the market. Sometimes it sits alongside a roast chicken or a piece of fish. Sometimes it is the meal, with bread and cheese and a glass of something cold. I wrote it down in the notebook last February: watercress, blood orange, red onion, Tuesday. The rain had been going all day. The salad was the brightest thing in the kitchen.