I don't know where this recipe originally came from, but I have a copy my mother hand wrote on an index card. It's a recipe index card, which says:
RECIPE: Beet Relish
From the Kitchen of: Grandma Swingle
2 c. coarsely grated beets (cooked)
2 tbsp chopped red onion
2 tbsp red wine vinegar
1 tsp sugar
2 tbsp dijon mustard
3 tbsp veggie oil
salt and pepper
Combine all ingredients in a small bowl and blend well. Chill thoroughly.
This is a great side dish - it seems to go with everything and adds that beautiful magenta color to your plate. It's tangy, with the underlying sweetness of the beets and that dab of sugar.
As far as the beets go, I prefer to roast them before grating. I usually cut them in half and place them cut side down on a baking sheet lined with tin foil and stick it in the oven for as long as it takes. I'd say 400 degrees or so. Let them cool and the skins should peel right off. Consider gloves or you'll end up with pink fingers. I always do.
End up with pink fingers.