Wash the beetroot, but do not peel or prepare so that the juice does not leak out during baking. Pat dry and place in a small gratin dish. Drizzle with a little olive oil and lightly salt.
Bake in the oven preheated to 200 ° C for about 45 - 50 minutes. Allow to cool slightly. In the meantime, stir all the ingredients for the vinaigrette well.
Carefully peel the beetroot, cut in half and cut into slices about 2 mm thick. Halve the avocado, remove the stone and peel. Cut crosswise into approx. 2 mm thin slices.
Lay the beetroot and avocado slices alternately, brick-like on 4 plates. Immediately drizzle with the dressing and sprinkle with the basil.
If you want to go a little faster, you can also use already cooked (vacuum-packed) beetroot. But if possible not the ones from the glass.
As an alternative, you can also sprinkle mozzarella pearls on top or diced feta.