Preheat the oven to 180°C.
Scrub the beetroot with a veggie brush or a clean cloth. Place on a sheet of greased foil, then fold in the sides and seal. Transfer to a baking tray.
On the same tray, drizzle the onion with the oil and sprinkle on a little salt. Bake for about 30 minutes, or until the beetroot are tender and the onion is golden. (Test the beetroot with a skewer.)
For the dressing, mix all the ingredients in a bowl. Set aside. When cool enough to handle, cut up the beetroot and place in a bowl with the onion, almonds and radicchio. Drizzle with the dressing and gently toss.