Preheat oven to 425°F. Remove greens and bottom roots from beets. Wrap beets with foil. Bake 45 minutes to 1 hour or until tender when pierced with small knife. Cool until able to handle. Peel beets.
Meanwhile, melt butter in small saucepan on low heat. Add flour, whisking until well blended. Stir in 1/2 cup of the orange juice until smooth. Whisking constantly, bring to boil on medium heat. Remove from heat. Pour into small bowl. Whisk in remaining 1/2 cup orange juice. Stir in sugar, lemon juice and 1/2 teaspoon of the tarragon. Stir occasionally until sauce is completely cooled.
Mix goat cheese, 1/4 cup of the pistachios and remaining 1 teaspoon tarragon in small bowl until well blended.
Cut beets into thin slices (no more than 1/8-inch thick). Using cookie cutters, cut beet slices into decorative shapes, if desired. Spoon 1/2 to 1 teaspoon filling onto half of the beet slices. Cover each with a second beet slice to create “raviolis”. To serve, spoon about 3 tablespoons Tarragon-Orange Sauce onto each plate. Arrange 3 to 4 "raviolis" in the sauce. Sprinkle with remaining 1/4 cup pistachios.