Preheat the oven to 190C/375F/gas 5. Spread a thin layer of sea salt on a large piece of foil. Arrange the beetroot on top and seal inside the foil. Bake for 45 minutes to 1 hour until they are tender and can be pierced easily with a knife.
Meanwhile, peel two of the oranges, remove the pith and cut into segments, catching the juices in a bowl. Squeeze the juice of the third orange into a bowl. Ass the white wine vinegar and oil and then whisk to combine. Season to taste.
Remove the beetroot from the oven. Unwrap the foil parcel and leave the beetroot to cool slightly. While the beetroot are still warm, peel them with a small knife, then cut into chunks or slices. Arrange the beetroot, orange segments, watercress and red onion rings on a platter or individual plates and drizzle over the dressing to serve.
- 450g (1lb) raw beetroot, washed and dried, with the tops removed
- 3 large oranges
- 1 teaspoon white wine vinegar
- 100g (4oz) watercress, woody stems removed
- 1 small red onion, thinly sliced into rings
- sea salt and freshly ground black pepper
- 4 tablespoons extra virgin olive oil