Toast the walnuts in the oven at 375 degrees for 5-7 minutes, let cool, and coarsely chop. Cut off the beet greens, and discard the stems. Wash the greens and cut into strips, about 1/2 inch wide. Scrub the beets but don’t peel them. Steam or boil until tender, about 30 minutes. (You can rub the skins off at this point, or leave them on.) Allow the beets to cool slightly, then slice them and toss with lemon juice, vinegar, one tablespoon of the olive oil, and salt to taste. In a large skillet, heat the remaining oil over medium heat. Add onion and saute for 3 minutes. Add the greens and cook, stirring, until wilted but still robust. Blend the beets and greens and garnish with walnuts.If not avoiding dairy, sprinkle some crumbed sheep’s milk or goat feta on top before serving.