Remove roots and leaves from the beets, scrub gently and roast at 400 degrees or until tender. This will take about 40 minutes to 1 hour or a little longer, depending on the size of the beets. Once tender, remove from the oven and allow to cool. Using paper towels--so as not to stain your hands--peel the beets, slice and set aside.
On a sheet pan in the oven, toast the hazelnuts until they turn golden brown and the smell of roasted nuts fills the house. Allow to cool and chop in a food processor so they are lightly crushed.
Combine all dressing ingredients, except the olive oil, in a stainless steel saucepan and simmer slowly for about five minutes. Adjust seasoning with salt, pepper, vinegar and sugar as desired.
Add the olive oil to dressing, and toss gently with the beets, hazelnuts and red onions and adjust seasoning as desired.