Pre-heat oven to 350 degrees. Toss beets, salt, and oil together in mixing bowl. Put them in a high sided roasting pan and add enough water to cover beets half way. Cover roasting pan with aluminum foil. Bake in oven until fork tender, or about 30 to 45 minutes. Allow to cool 5 to 10 minutes. Use a clean kitchen towel to rub the skin off the beets. Cut into wedges. Pour juices over the beets as they cool. Refrigerate until thoroughly chilled.
For the Brittle:
Boil the honey, water and sugar until just before caramel, add in the walnuts and stir continuously, until walnuts are toasted and sugar has reached caramel stage.
Carefully stir in margarine, followed by vanilla, salt, and baking soda. Quickly spread thinly on parchment paper and let cool completely. Bake into desired size shards.
To Assemble the Salad:
Place beet wedges in a medium size bowl, add oranges, grapefruit, and olive oil, toss to coat and season with salt and pepper to taste.
Garnish with walnut brittle and fresh greens.
*Please note to roast red beets separate form all other beets. They will discolor the other color.