Walnut Orange Passover Sponge Cake

12-14 servings. Spoon batter into a 10-inch tube pan lined in the bottom with baking parchment or greased brown paper. Place in a preheated 375-degree oben and immediately lower heat to 325 degrees. Bake until cake springs back to the touch, about 50 minutes. Remove from oven, let cool well before inverting/removing. (it helps to run a flat knife around the edge to separate cake from pan.) For the passover confectionrs' sugar: Place sugar and potato starch in a food processor and process until blended, about 3 minutes. Use as a garnish by sifting over cake lightly and arrange shreds of aorange peel on top. (regular conf. sugar includes cornstarch, which is a by-product of corn, which most authorities forbid.)