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["Put sugar into a large mixing bowl, then set aside 1/4 cup. ""You need a really big bowl to give you enough room, later, to fold the batter without deflating it."" Weigh in or add corn and rice flours to bowl. Add baking powder and salt, then egg yolks, oil, and 1/2 cup water. Add zest of 1 orange and whisk to blend thoroughly. Set batter aside 15 minutes to hydrate corn flour.", "Meanwhile, position a rack in lower third of oven and preheat oven to 325u00b0.", "Combine egg whites and cream of tartar in bowl of a stand mixer. Using whisk attachment, beat whites on medium-high until they're creamy white and the beater leaves tracks. Slowly sprinkle in remaining 1/4 cup sugar, beating on high speed just until egg whites hold a firm peak when you lift the beater (they should not be dry). ""If you're in doubt, think about the egg whites as balloons. The more beaten and expanded they are, the more likely they are to break in the oven (since the heat will expand them even more). Underbeating is better than overbeating.""
