Method
Peel the beetroot (beets) then slice each one into very thin rounds. You can do this with a very sharp knife or, if you are feeling brave, a mandolin. Either way, they shouldn’t be thicker than a couple of millimetres (¾in). Place the beetroot rounds in a large bowl.
Quarter, core and slice the apples into thin wedges and add these to the bowl with the beetroot. Trim away the skin from the wedge of squash then use a peeler to pare nice broad thin ribbons from the squash into the bowl. Keep peeling until you can’t peel any more; save any unpeelable squash for stock or soup making. Add the lemon zest and juice to the bowl along with some salt and pepper, then tumble everything together. Set the bowl aside for 15–20 minutes.
Meanwhile, combine all the ingredients for the dressing in a jar or bowl, with salt and pepper to taste, and give them a good shake or a stir.
To serve, spoon half the dressing over the salad and stir it through lightly. It doesn’t have to coat everything at this point. Lift the salad out onto a large plate or platter and spoon over the remaining dressing. Scatter over the extra tarragon leaves and bring to the table.