Fresh Orange Sponge Cake

(one 10-inch tube cake). Preheat the oven to 350F. Combine the flour and salt and sift them together twice; set aside. Put the egg whites into a large mixing bowl and beat until foamy. Gradually add 1/2 cup of the sugar, and continue beating until the whites are stiff but moist, and stand in peaks that droop slightly when the beater is lifted. In a separate mixing bowl, beat the egg yolks until they have thickened slightly, then slowly add the remaining 3/4 cup sugar, and continue to beat until the mixture is thick and lemon-colored. Add the orange rind and juice and blend well. Sift the flour over the yolk mixture, and stir gently until smooth, with no drifts of flour visible. Gently stir in one quarter of the beaten whites. Pour the remaining whites on top, and fold them into the yolk mixture until smooth and blended. Spread the batter evenly in an ungreased 10-inch tube pan. Bake for about 40 minutes, or until a straw inserted in the middle of the cake comes out clean. Remove the cake from the oven and invert it. Let cool completely before removing from the pan. Mountain Frosting 1 1/2 cups sugar 1/2 cup water 1/4 teaspoon cream of tartar 1/4 teaspoon salt 3 egg whites (about l/2 cup) 1 1/2 teaspoons vanilla extract Combine the sugar, water, cream of tartar, and salt in a saucepan and set over high heat, gently swirling to mix the ingredients. Let boil, swirling occasionally, until mixture is perfectly clear, about 4 or 5 minutes. Clap the lid on the pan and let cook for 1 minute. Uncover and attach a candy thermometer, not letting the tip touch the bottom of the pan. Let the syrup boil, uncovered over high heat until it reaches 240'F. Meanwhile start beating the egg whites in a large bowl to stiff but moist peaks. When the syrup is ready, continue beating at moderately high speed, and with your other hand pour the syrup on in a thin, steady stream. Continue beating for 2 or 3 minutes more until the frosting has cooled a little and is stiff enough to stand in tall peaks. Beat in the vanilla. You use this generously and will have enough to fill and frost two 8-inch layer cakes or a 10-inch tube cake. Orange Mountain Frosting Decrease the water to 1/4 cup, and add l/4 cup freshly squeezed orange juice and 1 tablespoon grated orange rind to the syrup before you cook it. Lemon Mountain Frosting Decrease the water to 1/3 cup and add 2 tablespoons lemon juice and 1 tablespoon grated lemon rind to the syrup before cooking it.