This beautifully flavored gluten free brown sugar blood orange angel food cake elevates angel food cake with the bright sweetness of citrus juice and zest. The addition of brown sugar is an unexpected touch.
Preheat oven to 350℉. Whisk together the flour and ¾cup brown sugar. Sift twice.
Put egg whites into the bowl of an electric mixer fitted with the whisk attachment. Beat on medium speed until foamy. Add cream of tartar and salt. Raise speed to high, and beat until soft peaks form. Sprinkle half the remaining ¾ cup brown sugar over the egg white mixture, and beat until combined. Sprinkle the remaining brown sugar over egg white mixture, add the orange extract and juice, and beat until stiff, glossy peaks form.
Transfer egg white mixture to a large bowl. Fold in flour mixture in 3 batches, folding in zest with last batch.
Spoon batter into a clean, ungreased 10-inch tube pan (not nonstick) with a removable bottom. Run a knife through the batter to eliminate air pockets. Bake until the cake is golden and springs back when lightly touched, about 45 minutes to 1 hour.
Invert pan onto its legs or over a narrow-neck bottle; let cool for at least 1 hour. Reinvert, and run a knife around sides and tube to loosen; remove the sides. Run a long knife along bottom of cake, then remove the tube. Store the cake, well wrapped, on the counter at room temperature for up to 5 days.